How to recreate a particular image from PCA from a database of images?

Please forgive if this is a repeat but I couldn't find a similar question (at least as it pertains to me).  I have a database of 30,000 images of digits (0-9). Every image is 28*28. So, every image is represented by a row of 785 columns  with the first column as a label (whether the digit is 0 or 1 or … 9) and columns 2: 785 having a value of black(from 0-255).  Now, I have the pca using pca <- prcomp(df[, -1], center=TRUE) with 784 PCAs. I also have a mean of all the digits using meanDig <- apply(df[, -1], 2, mean) (I don't know if this mean is useful or not).  Now, I am being asked to recreate the '100th' image from the database using first 15 PCs.  I understand from  and other related questions how to recreate one single image from the PCA of that single image.  But if I have PCA of a collective of 30000 images, is it possible to recreate the one single image?  I tried:  recreation <- pca$x[, 1:15] %*% t(pca$rotation[, 1:15]) # which gives me a matrix of 23520000 elements. # I am not sure how I can recreate a 28*28 image? # Then I thought maybe I can do this for the "15th" row: recreation <- pca$x[100, 1:15] %*% t(pca$rotation[100, 1:15]) # but I am not sure what this even means.   Any suggestions?     Edit #1   I am adding more information after taking @chechy_levas suggestions into consideration.  # Read the data: df <- read.csv("classDigits.csv") head(df[, 1:5])  label pixel0 pixel1 pixel2 pixel3 1     2      0      0      0      0 2     4      0      0      0      0 3     7      0      0      0      0 4     2      0      0      0      0 5     8      0      0      0      0 6     9      0      0      0      0  # Calculate PCA: pca <- prcomp(df[, 2:785], center = TRUE) head(pca$rotation[, 1:3])                  PC1           PC2           PC3 pixel0  2.219274e-20 -5.732181e-19  6.287447e-20 pixel1  2.081668e-17  1.110223e-16  2.081668e-17 pixel2 -1.942890e-16  0.000000e+00  4.857226e-17 pixel3 -1.387779e-16  1.110223e-16  4.336809e-17 pixel4  5.551115e-17  0.000000e+00 -1.387779e-17 pixel5  1.110223e-16  1.387779e-16  2.081668e-17  # calculate the mean digit meanImage <- apply(df[, 2:785], 2, mean)  # mean image looks like this:     # The 15th image for reference:     # recreate the image at row 15 with 15 PC. img15 <- pca$x[15, 1:15] %*% t(pca$rotation[, 1:15]) img15 <- img15 + meanImage  # Image with 15 pc:     # recreate the image at row 15 with 100 PC. img15 <- pca$x[15, 1:100] %*% t(pca$rotation[, 1:100]) img15 <- img15 + meanImage  # Image with 100 pc:     # Image with 200 PC


Is there any lite Ubuntu version for an old PC?

I'm currently stuck with an old PC with amd-core processor and 2GB RAM. Windows isn't doing well so I've switched to Linux and want to know if there is any lite version of Ubuntu available for basic use.


Why was Jesse angry with Walter in the last few episodes when he was getting picked to be relocated in Alaska?

Why was Jesse angry with Walter in the last few episodes of Breaking Bad when he was getting picked to be relocated in Alaska?   He already knows that Brock was poisoned with lily (from doc report), and from that he got to know that Gus didn't poison Brock and neither did Walter (because Walter had destroyed the plant of lily).  There is no evidence in the series by which Jesse could be knowing Walter's possession of the lily plant. Even if Walter stole ricin, there could be a possibility (which Jesse should have thought) that the stolen ricin can be used for any future endeavors (killing Hank perhaps). I mean what made Jesse so strongly believe that it was Walter who made Huell to pick pocket a ricin cigarette from him (because the second ricin cigarette, made by Walter was found in the Roomba in Jesse's house)?   Also Jesse was pretty sure that Walter only did the conspiracy of poisoning Brock where it was already established and known to him that poisoning was done from lily flower (doc report).  Jesse was definitely strongly believing that it was Walter who ordered for pick pocketing. But why does ricin poisoning matter at all now? Such that he made desperate attempts twice to burn down Walter's house.


the exponent of the highest power of p dividing n!

The formula for the exponent of the highest power of prime $p$ dividing $n!$ is $\sum \frac{n}{p^k}$, but the question is $n=1000!$ (really, it has the factorial) and $p=5$.  When I use Wolfram Alpha , I panicked because the number has $2,567$ decimal digits.  I think if I write this number I'd need paper all the way to the Amazon.  Perhaps I misunderstand the formula?


Is calling a linear-equation a linear-function, misnomer or completely wrong?

From my college life, I remember many professors used to call a linear-equation a linear-function, however:  A standard definition of linear function (or linear map) is:  $$f(x+y)=f(x)+f(y),$$ $$f(\alpha x)=\alpha f(x).$$  Where as linear equation is defined as:  $$f(x)=mx+b.$$  So, linear-equation is NOT a linear-function, according to the definitions defined above.  Though, for $b=0$ the linear-equation becomes a linear-function, but it is not true in general.  Question: Is it misnomer to call a linear-equation a linear-function, or it is completely wrong to say that? And linear-equation must be considered strictly as an affine-mapping.


How do I get rid of particular pdftex warning message?

Here is a minimal example that showcases my problem:  \documentclass{article}  \usepackage{amsthm} \usepackage{hyperref} \usepackage{cleveref}  \newtheorem{thm}{Theorem} \newtheorem{lem}[thm]{Lemma}  \begin{document}  \begin{lem} Lemma \end{lem}  \end{document}   The warning I get is the following:  [1pdfTeX warning (ext4): destination with the same identifier (name{thm.1}) has been already used, duplicate ignored  \AtBegShi@Output ...ipout \box \AtBeginShipoutBox                                                    \fi \fi  l.16 \end{document}                    {<install dir>/MiKTeX/2.9/pdftex/config/pdftex.map}]   I know that it is just a warning and that, my document will still work perfectly fine with regards to cross-referencing and hyperlinking, but I would still like to know why I am getting this warning and if anything can be done to fix it without removing functionality of the included packages.   Bonus question: Whats going on behind the scenes when this warning (or any generic 'destination with the same identifier (name{XXX.YYY}) has been already used, duplicate ignored') is produced, as this is not limited to theorem environments.  From log file:  Package: amsthm 2004/08/06 v2.20 Package: hyperref 2011/04/17 v6.82g Hypertext links for LaTeX Package: cleveref.sty 2011/03/22 v0.17.9 Intelligent cross-referencing Package cleveref Info: `hyperref' support loaded on input line 2157. Package cleveref Info: `amsthm' support loaded on input line 2300.


Why do I get one extra wrong solution when solving $2-x=-\sqrt{x}$?

I'm trying to solve this equation:  $$2-x=-\sqrt{x}$$ Multiply by $(-1)$: $$\sqrt{x}=x-2$$ power of $2$: $$x=\left(x-2\right)^2$$ then: $$x^2-5x+4=0$$ and that means: $$x=1, x=4$$    But $x=1$ is not a correct solution to the original equation.  Why have I got it? I've never got a wrong solution to an equation before. What is so special here?


Evaluate $L=\displaystyle\lim_{n \rightarrow \infty} \left(1+\dfrac{1}{a_1}\right) \left(1+\dfrac{1}{a_2}\right) \dots \dots \left(1+\dfrac{1}{a_n }\right)$ where $a_1=1$ and $a_n=n(1+a_{n-1}), \ \forall \ n \geq 2$   By rewriting $L=\displaystyle\lim_{n \rightarrow \infty} \left(\dfrac{1+a_1}{a_1}\right) \left(\dfrac{1+a_2}{a_2}\right) \dots \dots \left(\dfrac{1+a_n}{a_n }\right)$ and observing that $1+a_m=\dfrac{a_{m+1}}{m+1}$, I reduced $L$ to $$L=\displaystyle\lim_{n \rightarrow \infty}\dfrac{a_{n+1}}{(n+1)!}$$  I do not know know how to proceed further.   Solutions and hints in the right direction would be appreciated.


fsck.ext4 is running in the background at 0% CPU. Is it done?

Is there a way to check if fsck is completed? I sent it to the background but don't know how to get it back.  I'm on a Raspberry Pi.


Why cannot find read /run/user/1000/gvfs even though it is running as root?

Can someone tell me what I'm doing wrong, what this is, or how to fix it? I'm running Fedora 18 and getting the error shown  [root@servername /]# find . -name ngirc find: `./run/user/1000/gvfs': Permission denied [root@servername /]#  [root@thinktank /]# pwd / [root@thinktank /]# ls -ltr ./run/user/1000 ls: cannot access ./run/user/1000/gvfs: Permission denied total 0 d?????????? ? ?    ?      ?            ? gvfs lrwxrwxrwx. 1 root root  17 May 28 12:30 X11-display -> /tmp/.X11-unix/X0 drwx------. 2 kal  kal  120 May 28 12:30 keyring-QjDw4b drwx------. 2 kal  kal   40 May 28 12:30 gvfs-burn drwx------. 2 kal  kal   60 May 28 12:30 krb5cc_5f0bcaf94f916d6b61696e2251a4dbb3 drwx------. 2 kal  kal   60 May 28 18:25 dconf


How can I transfer windows partitions to ubuntu?

I have an Asus laptop and it had windows 10 by default and it has 512 GB SSD. I shrinked about 60 GB from a windows drive and I formatted it as unallocated partition. I installed Ubuntu on that 60 GB. Now I want to change the partitions again and allocate a bigger size to ubuntu. Now I have about 200 GB of unused memory on windows and need more space on ubuntu. Note that I do not want to mount them in read-only mode. Is there a solution to do that? EDIT: I am dual-booting now and I want to have both windows and ubuntu on my laptop. But the partition allocated to linux is only 60 GB out of 512 GB of SSD. I want it to be more. [Screenshot link is attached.] EDIT: I turned off device encryption in windows and now I can access windows drives and files from linux. But they are mounted in read-only mode and I can not create files, etc. How can I now access them (ex. only one drive), like the main ubuntu drive?


Excel-Count number of visible cells containing certain string

I have a sheet in which I first apply a filter to a certain column to show "Unique records only". Now I have a column which contains, for e.g., values like:  Applepie Applesauce Crabapple Banana Mango   What I need is the count of all visible cells containing the word "Apple". Note that this should exclude the hidden (filtered out) cells. Now I have found out a formula:  `=SUMPRODUCT(SUBTOTAL(3,OFFSET(Sheet1!A:A,ROW(Sheet1!A:A)-MIN(ROW(Sheet1!A:A)),,1))*(Sheet1!A:A="<Text to search>"))`   However the problem with this one is this formula searches for the entire text. NOT just a part of it. How do I modify this formula to return count of cells containing "Apple" i.e. for this example it should return 3 as the result.


Is there a command like head but for line truncation?

Linux's head selects a number of lines from the top of a file.  Is there a command that selects a number of characters from the front of a line?  The use case behind the question is this: I want to head the first 10 lines from a file, but each of those 10 lines is extremely long and contain lots of white space, making it hard to discern where the line breaks are.  It would be much easier to get a general idea of the contents of the file if I could head the first 10 lines, but only view the first 50 characters of each line.


I want to typeset something like this: 3.0 × 3.0 × 0.9 mm  How can I do that in LaTeX (using siunitx package)?  So far, I have this:  \num{3.0} × \num{3.0} × \SI{0.9}{\milli\metre}   But probably someone else knows a better solution.


Unfortunately, I don't have a lot of details on this story; I can't even recall when I read it - except that it was almost certainly over 30 years ago. It may have been a story in an anthology, but I won't swear to that; I have the impression that it may actually have been novella-length.  The basic plot element was that it was illegal to create music in the social context of the story, and the protagonist did so. The only real detail from the story that I recall is a scene where they stopped him from singing by placing a device against his throat that disabled his larynx, and later had to stop him from playing by (painlessly) amputating his fingers.


Office Online integration with SharePoint 2016

I would to ask if it is possible to integrate Office Online from O365 with SharePoint 2016 instead of using Office Online Server?  Thank you,


How did Jane became worthy of holding Thor's hammer?

In the comics, Jane became the new Thor, but how did she become worthy of holding Mjolnir?


How does increasing the distance between 2 copper plates in a circuit affect the capacitance?

We have been told that the voltage decreases, but not been given a proper explanation by my teacher. Can anyone shed some light on this?  Also, does increasing the distance between the plates of a capacitor decrease the capacitance, and hence reduce the time it takes for it to be discharged, since t=RC, and C gets smaller with a bigger distance between the plates? Is my understanding of the above part correct?


Do anybody have idea about full form of rc.d at?    /etc/rc.d   It contain scripts to  is used to control the starting, stopping and restarting of daemons. But what exactly meaning of rc here, do anyone have clue?


Does there exist some command for subtitles in the \maketitle thing?


Prove that $p(x)=(x-1)(x-2) \cdots (x-n) + 1$ is irreducible over $\mathbb{Z}$ for all $n \geq 1$, $n \neq 4$.  I do not clearly see how to solve this problem and what is so special about the integer $4$ here?  Thanks for your help in advance


How to resize windows with alt+right click instead of alt+middle click in Ubuntu 13.04

The title says it all. I want to resize windows with an right click while holding the alt key, instead of the new default alt+middle click.  I have found no way to enable this behaviour in 13.04. The gconf-Key suggested in this , doesn't seem to exist any longer.


Has the Stack Exchange buying option been closed?

Can I still buy from Stack Exchange to create a site like mathoverflow.net for local intranet use?  I think this option has been removed, just want to confirm. What are the other options that I have?


Is it possible to make hidden files or folders show up on the desktop?

Is there any way to make hidden (.name) files and folders visible from the desktop?


I'm interested in rendering Visualforce as advanced_pdf, but I can't find any new details since it went .  Are there any updates?


Symlinks point to the same executable target, but do different things

I have vim-athena package (the same is observed for vim-gtk) in my Debian machine.  Running vim spawns Vim in the terminal. Running gvim spawns a new window with Vim in a Athena GUI.  But what is vim and gvim? Symlinks pointing to a same target. $ readlink -e "$(type -p gvim)" /usr/bin/vim.athena $ readlink -e "$(type -p vim)" /usr/bin/vim.athena  And that final target is a binary. $ file --brief /usr/bin/vim.athena ELF 64-bit LSB shared object, ...  How can it be that vim and gvim do different things if both resolve to the same binary? Background: I was changing my default editor via update-alternatives --config editor. In the list, there are vim.tiny and vim.athena, but even if I select the latter, Vim always opens in the terminal, not in a separate GUI.


Crew members of a space ship turned to stone

I saw an old B&W sci fi movie involving several crew members of a space ship who have been turned to stone\petrified. When another crew member ventures outside to investigate there is a big sphere outside the ship which draws him inside against his will.  I don't remember if the sphere used tentacles or some invisible force.


Separating template class definition from declaration - explicit instantiation

I have a .h and .cpp file Foo.h template<typename T> class Foo { public:   void g();   void h(); };  Foo.cpp #include <iostream> #include "Foo.h" template<typename T> void Foo<T>::g() {   std::cout << "Foo<T>::g()\n"; } template<typename T> void Foo<T>::h() {   std::cout << "Foo<T>::h()\n"; }  The above two files are in abc/def directory and I have the implementation in a different cpp file Foo-impl.cpp #include <../../Foo.cpp> template class Foo<int>;  This Foo-impl.cpp is in abc/ghi/jkl directory. But when I use #include <abc/def/Foo.cpp I get an error saying that the file doesn't exist. But when I use #include <abc/def/Foo.h>, I don't get file doesn't present erro (the file is identified by the compiler) but I get linker error. I am using the implementation as per  Why does it work with <../../Foo.cpp> and why not with <abc/def/Foo.cpp. How should I make it work ?


Object on screen but not showing up on screen collection/hiearchy

I have 2 cylinders and one cube in my scene. The cube is in the hierarchy, whereas the cylinders are not. Can someone explain to me why this is happening? It's kind of a pain to have to select every single vertice every time I want to move it!


Object Reference Error trying to call a Method from a Class. Error code CS0120

I'm trying to learn programming in general using C# as my first language so please bear with me as I do not know how to exactly asked what I need to ask. Basically I'm following along code from a YouTube video and I hit a brick wall. Here's the entire source code using System; using System.Collections.Generic; using System.Linq; using System.Text; using System.Threading.Tasks;  namespace CoffeeNCodeStructures {     public class Program     {         public class Person         {             public string name;             public int age;              public Person(string name, int age)             {                 this.name = name;                 this.age = age;             }              public string PrintPerson()             {                 return "Name: " + name + " - Age: " + age;             }         }         static void Main(string[] args)         {             List<Person> people = new List<Person>();              for (int i = 0; i < 2; i++)             {                 Console.WriteLine("Please enter your name: ");                 string name = Console.ReadLine();                  Console.Write("Please enter your age: ");                 int age = Convert.ToInt32(Console.ReadLine());                  people.Add(new Person(name, age));             }              foreach (var item in people)             {                 Console.WriteLine(Person.PrintPerson());             }              Console.ReadLine();         }     } }  Visual Studio is throwing me this error  error CS0120: An object reference is required for the non-static field, method, or property 'Program.Person.PrintPerson()'  The issue is in this code block specifically             foreach (var item in people)         {             Console.WriteLine(Person.PrintPerson());         }  Person.PrintPerson() won't work. What am I doing wrong in the code? I hope this question isn't to vague or bad. I'm new and really wanna understand the code in front of me here that I am screwing up. Thanks!


On my Canon T7i, in the viewfinder, there is a circle that shows up when focus has been achieved. That is not functioning correctly now.  I am using it with a 24mm f2.8 Canon lens.  The focus indicator was initially not coming on at all. Then I realized if I focus on my pants it would come on. I then tried to focus on any other surface, all of which the camera easily achieved focus, but the indicator did not show. All the surfaces I focused on were flat and textured, very easy to focus on, but the camera was not searching for focus. It only showed the indicator when I focused on my pants.  Is it possible that either the camera or the lens is broken? Or am I missing a setting I can change?


Prove that $\alpha\in \mathbb{Z}[\sqrt{2}]^*$ if and only if $N(\alpha)=\pm 1$.

How would I show that an element $\alpha$ is in $\mathbb{Z}[\sqrt{2}]^*$ (the invertible elements of $\mathbb{Z}[\sqrt{2}]$) if and only if the norm of $\alpha$ is $\pm 1$? I did not see this as a duplicate at first because I thought that $1$ and $\pm 1$ needed different ways of proving, but it turns out that if $N(\alpha)$ divides $1$, then it can be negative or positive.


I am provided the following details (see picture) about a sample whereby $x$ is logarithm of income. How do I calculate the sample variance from this information?


Is it alright to pay real money for useful help?

Possible Duplicate:          I'm really stuck. My post  isn't getting any help yet. I'd be thrilled to pay a few bucks for a solution. I'm thinking of posting the following. But before I do, this seems like a good place to check first to see if something like this is ok. So, would the post below be ok?    I've been working on solving the problem described  for too long. I will pay $40 to the first person who provides the answer I need to fix the problem.  Yes, real actual money for real help.  The conditions of my offer are:   Yes, you'll just have to trust me to actually pay up. But you can - I'm good for it. You'll need a PayPal account where I can send you the money. I'll pay the first person to post a usable solution. I'm the sole judge on who's first and what I consider usable. When I have a usable solution, I'll post a reply inviting the person providing the answer to email me their PayPal account info so I can pay you. If you're skeptical (very reasonable) feel free to email me at the above address if you'd like reassurance that  my offer is real.


How can I enable 3D acceleration for Ubuntu as a VMWare guest?

I use Ubuntu on an iMac 8,1. I haven't been able to figure out how to enable 3d support for VMware Workstation 10. Ubuntu lists several Nvidia options but I so far they lock up the screen on log in.  What are some tools for me try?


A series about the Seventh son of a seventh son and a bullet that will always find its mark

I am looking for the name of a series of book.  In the world described in those books, magic exists, and it is also told that the 7th child of a family will be extremely proficient with it.  In the first book, we are following the story of a family, whose father is one of those 7th sons, but is nothing extraordinary when it comes to magic. At the start of said book we learn that his wife gave birth to a child which is their 7th (7th son of a 7th son).  But sadly it seems like the child died shortly after.    We also learn of another family, which is celebrating the birth of their newborn daughter, but during the celebration, an assassination takes place, and only the newborn daughter survives.  What was particular with this assassination is the fact that the killer used bullets, with a name inscribed on them. Those bullets are known to always find their way to the person their destined to.  After surviving this, the daughter was adopted by the first family.    A few traits of this world which can help identify the book :   While magic exists, it doesn't seems that everyone can be a mage, and only a few select ones can excel in it. The most powerful mage in the country is given a position of authority, and usually takes an apprentice amongst the most promising mages, and usually that apprentice will take that position after their master.   A few key events (in the first book) that can help :   After the assassination of the second family (which was something akin to royalty) a new government takes place. This government created a militia, which enrolled many young children to indoctrinate them.   At the end of the first book, we learn that one of those young children was, in fact, the seventh child of the first family (which they thought died at birth)  After a while, the new government learns about the whereabouts of the daughter of the second family, and sends assassins against her. So the first family (who adopted the daughter) decides to take refuge with their aunt, who is somewhat of a hermit and is living in a remote location.     If anyone is able to identify the book from this mess of a question, that would be really helpful.


How to remove "phone style" Gnome swipe to unlock

I need to remove the annoying new "locking" screen that shows a giant clock: I can't remove it with just moving the mouse (as with any other desktop environment), the animation is slow, and it isn't asking me for a password!  I managed to disable it, just to discover that now I can't lock my screen on purpose, so I can't go away from the computer.  Just to clarify, I want to:   After some time the screen could go black, but if I move the mouse or press any key then I can use it directly (like a normal screensaver). If I press super-L then it is locked, and I must type the password to unlock (like a normal lock screen).   I found several "solutions", but none seems to work:


Suppose to be in an arbitrary gravitational field and you are moving in it arbitrarily with a clock in your hand. In this general situation I ask: if I read the positions of the hands of the clock, what am I really measuring the proper time or a simple coordinate?


I want to ask about Linq. Can I discard change to database using Linq? For example, I've submit data to database, but I haven't use db.SubmitChanges(); syntax. Well, this is going to be hard to explain, so let's take a look for the example.  //the Code for insert the data to database db.myTable.InsertOnSubmit(insert);   So, if I want to submit to database, I have to use :  db.SubmitChanges();   But, what I want to do is to discard or cancel my insert data, so when I use db.SubmitChanges(); the data will not go to the database.  I'm so sorry if this is so confusing, I'm still beginner.


Playing skyrim cannot join Dark brothethood

I killed Grelod the kind without talking to anyone from the brotherhood does this mean I cannot join?


French characters not being displayed properly

I am using curl to pull in a news feed, however the french version is pulling in some weird characters.  For example "activitÃ©s" should be "activités"  $feed = curl_init($json); $options = array(    CURLOPT_RETURNTRANSFER => true,    CURLOPT_HTTPHEADER => array('Content-type: application/json'),    CURLOPT_POSTFIELDS => $feed ); curl_setopt_array($feed, $options); $news = curl_exec($feed); curl_close($feed);  $articles = json_decode($news, true);


Can we get x comment votes per y minutes, rather than one vote per 5 seconds?

I quite often will read a thread of comments, and want to vote up a few of them. I vote one up, read the next few comments, vote up another and get a *giant red box*.  I've seen that "You can only submit a comment vote every 5 seconds" box far too often. Can I vote for 12 comments per minute, rather than 1 comment every 5 seconds?


I was dual-booting Windows 10 and Ubuntu on my laptop for some time. A while back, my laptop died and had to be sent in for repair. Turns out there was some bug in the BIOS so that it had to be reinstalled. My SSD is untouched, though. It has not been wiped, and Windows has not been reinstalled.  The only problem is that I no longer get the purple boot screen where I can pick what OS to start. It just goes straight to Windows. My Ubuntu installation is probably still there, or at least my Windows partition is still smaller than the complete drive.  What do I need to do to be able to boot Linux again? My skill level is very low here, no idea how bootloaders or anything like that works.


If $U$ and $V$ are subspaces of $\mathbb{R^4}$, $(U+V)^{\perp}=(U^{\perp}\cap V^{\perp})$

As the title says, I would like to know if that equality is true if we consider $\mathbb{R^4}$.  I would write down my attempt, but I have no idea how to prove it, or how to choose a counterexample.   $(U^{\perp}\cap V^{\perp})$ are the vectors which are orthogonal to both $U$ and $V$, while $(U+V)^{\perp}$ are the vectors which are orthogonal to the linearly independent vectors of $U$ and $V$


File access time not being updated. Is caching the reason?

Please see below output. After creating a file, and doing a grep for the fist time --> the file access time is getting updated. But on subsequent greps the file access time is not getting updated. $ echo first line > b.txt  ~/wtmp/ttime$ stat b.txt    File: b.txt   Size: 11          Blocks: 8          IO Block: 4096   regular file Device: 804h/2052d  Inode: 1969341     Links: 1 Access: (0664/-rw-rw-r--)  Uid: ( 1000/       w)   Gid: ( 1000/       w) Access: 2020-09-06 17:36:01.091962795 +0530 Modify: 2020-09-06 17:36:01.091962795 +0530 Change: 2020-09-06 17:36:01.091962795 +0530  Birth: -  ~/wtmp/ttime$ date Sunday 06 September 2020 05:37:06 PM IST  ~/wtmp/ttime$ grep f b.txt  first line  ~/wtmp/ttime$ stat b.txt    File: b.txt   Size: 11          Blocks: 8          IO Block: 4096   regular file Device: 804h/2052d  Inode: 1969341     Links: 1 Access: (0664/-rw-rw-r--)  Uid: ( 1000/       w)   Gid: ( 1000/       w) Access: 2020-09-06 17:37:21.049046050 +0530 Modify: 2020-09-06 17:36:01.091962795 +0530 Change: 2020-09-06 17:36:01.091962795 +0530  Birth: -  ~/wtmp/ttime$ date Sunday 06 September 2020 05:38:23 PM IST    ## Second attempt searching for different letter  ~/wtmp/ttime$ grep l b.txt  first line    ~/wtmp/ttime$ stat b.txt    File: b.txt   Size: 11          Blocks: 8          IO Block: 4096   regular file Device: 804h/2052d  Inode: 1969341     Links: 1 Access: (0664/-rw-rw-r--)  Uid: ( 1000/       w)   Gid: ( 1000/       w) **Access: 2020-09-06 17:37:21.049046050 +0530** Modify: 2020-09-06 17:36:01.091962795 +0530 Change: 2020-09-06 17:36:01.091962795 +0530  Birth: -  Is this because the file is cached in memory and the access is done from memory. If that is the case is there a way to tell grep or any command to not use cached version but access it from file system.


Jagged/Black edge artifacts when modeling

I don´t know if this is a bug only to me or a common problem, for I don´t know why it occurs.  I had a problem once before where some edges of my model got jagged with black holes when switching to rendered mode (or actual rendering). Answers I got said that I modeled in too much detail or too small, and used the combination Subdiv Modifier/Auto Smooth/sharp edges wrong.  Now I have a way more problematic thing. I have a really simple scene, but most of the edges have this annoying jagged problem. I build this model in a higher scale (since the last one was too small).  I used the Subdiv Modifier/Auto Smooth/sharp edges again, but if I toggle on/off the Subdiv Modifier/Auto Smooth/sharp edges/seams, shade smooth/flat, won´t help at all. These artifacts just keep showing.  Does anyone know why this occurs?  Shaded Flat and zoomed in for a better look on the artifact.      My hardware specs are   GPU: Asus M5A78L-M LX3 GPU: NVidia GTX 750 StormX OC CPU: AMD FX6300 @ 3,5 GHz 8 GB RAM Windows 7 Professional 64-bit


Trick Supertabular into Multicols in new command

I'm using supertabular in multicols enviroment using this trick  \let\mcnewpage=\newpage \makeatletter \renewcommand\newpage{%     \if@firstcolumn         \hrule width\linewidth height0pt         \columnbreak     \else         \mcnewpage     \fi } \makeatother   I'd like to put that code into \newcommand - I've tried this:  \newcommand{\TrickSupertabularIntoMulticols}{ \let\mcnewpage=\newpage \makeatletter \renewcommand\newpage{%     \if@firstcolumn         \hrule width\linewidth height0pt         \columnbreak     \else         \mcnewpage     \fi } \makeatother }   but when i use my \newcommand it doesn't work - table is in only one column. What is the right way to define this command?  EDIT: examples  this works fine but i generate multiple multicols in the document so I want to put that trick code into single line comand   \documentclass{article} \usepackage{supertabular,multicol}  \newcount\n \n=0 \def\tablebody{} \makeatletter \loop\ifnum\n<100         \advance\n by1         \protected@edef\tablebody{\tablebody                 \textbf{\number\n.}& shortText                 \tabularnewline         } \repeat \makeatother  \begin{document} \begin{multicols*}{2} \let\mcnewpage=\newpage \makeatletter \renewcommand\newpage{%         \if@firstcolumn                 \hrule width\linewidth height0pt                 \columnbreak         \else                 \mcnewpage         \fi } \makeatother  \begin{supertabular}{|l|l|} \tablebody \end{supertabular} \end{multicols*} \end{document}   and this doesn't work  \documentclass{article} \usepackage{supertabular,multicol}  \newcount\n \n=0 \def\tablebody{} \makeatletter \loop\ifnum\n<100         \advance\n by1         \protected@edef\tablebody{\tablebody                 \textbf{\number\n.}& shortText                 \tabularnewline         } \repeat \makeatother  \newcommand{\TrickSupertabularIntoMulticols}{ \let\mcnewpage=\newpage \makeatletter \renewcommand\newpage{%         \if@firstcolumn                 \hrule width\linewidth height0pt                 \columnbreak         \else                 \mcnewpage         \fi } \makeatother }  \begin{document} \begin{multicols*}{2} \TrickSupertabularIntoMulticols \begin{supertabular}{|l|l|} \tablebody \end{supertabular} \end{multicols*} \end{document}


When automating UI tests with Selenium, it is often not absolutely clear what method and what locator to use to locate an element. Some locators are less reliable, less readable than others. And, usually, there are a lot of options to get to a desired element.  To be specific, here are some things we've enforced (with ESLint) in our UI test automation project (using Protractor for testing an AngularJS application):   no bootstrap classes used inside CSS selectors (the idea is to use as less UI/layout-specific things to locate elements as possible) no internal angular classes inside CSS selectors - things like ng-scope or ng-binding are pure-technical and should not be used inside locators do not use "xpath" unless absolutely necessary (encouraged by this )   The Question:  What other recommendations are there for locating elements in Selenium?


Is the set of real matrices diagonalizable in $\mathcal M_n(C)$ dense in the set of all companion matrices?

Let $\mathcal E=\{A \in \mathcal M_n(\mathbb R): A \text{ is of companion form} \}$. That is, $A$ has the following form \begin{align*} A=\begin{pmatrix}  0 & \cdots & 0& -a_{0} \\  1 & \cdots & 0 & -a_{1}\\ \vdots &\ddots & \vdots &\vdots \\ 0 &\cdots & 1 & -a_{n-1} \end{pmatrix}. \end{align*} Let $\mathcal D = \{A \in \mathcal M_n(\mathbb R): A \text{ is diagonalizable in $\mathcal M_n(\mathbb C)$}\}$. We know $\mathcal D$ is dense in $\mathcal M_n(\mathbb R)$. I am wondering whether $\mathcal E \cap \mathcal D$ is dense in $\mathcal E$. The set $\mathcal E$ is closed. It is not clear to me whether this statement is true.


Is the email notification from Apple that your device has been tracked using Find My iPhone a new feature?


/etc/shadow date of last password change—UTC or local time?

man 5 shadow gives the following description of the third field in each line:  The date of the last password change, expressed as the number of days since Jan 1, 1970. The value 0 has a special meaning, which is that the user should change her pasword the next time she will log in the system. An empty field means that password aging features are disabled.  Does this refer to times in UTC or the local timezone? In particular, if I want to calculate comparable numbers using something like $(( $(date +%s) / 86400 )), do I need to pass date the -u option?


Do I need a transit visa for a 23 hour layover in Amsterdam?

Does a South African citizen travelling from Canada to South Africa via Amsterdam, with a lay over of 23:50 need a transit visa?


Can I put 700c tires on rims made for 27 x 1.25"?

It's getting hard to find any selection for my old Avanti 12 speed. it currently uses 27 x 1.25 inch tires. Can I put 700c tires without needing to buy new rims?


Do internet bandwidth get used when I am using vpn or proxy?

In my country, most of porn sites are banned, so i choose VPN & proxy to browse, it means my ISP get change if i connect to VPN or proxy, so my Internet bandwidth get used when I connect to vpn or proxy?


Is a composite index also good for queries on the first field?

Let's say I have a table with fields A and B. I make regular queries on A+B, so I created a composite index on (A,B). Would queries on only A also be fully optimized by the composite index?  Additionally, I created an index on A, but Postgres still uses the composite index for queries on only A. If the previous answer is positive, I guess it doesn't really matter, but why does it select the composite index by default, if the single A index is available?


mount permission mechanism for file explorers

When I execute a script that uses the "mount" command, I need to enter my sudo password. However, I can launch a file explorer like nautilus and mount a filesystem from that application, without ever having to enter a password. What is the mechanism that allows some programs to execute commands that normally require root privilege?  My first instinct was that it is suid, but I changed the owner of a script to root and set the suid flag, i.e., "chmod 4777", but still I cannot perform things in the script that require root privilege.


How can I retrieve a .iso from an MSDN dreamspark account?

I am currently attempting to bootcamp my Macbook Air. As far as I have seen, bootcamp can only be installed via .iso. When attempting to download my version of Windows (Win7 Pro 64-bit) from the dreamspark website, it prompts me to download the Secure Download Manager (SDL) and after that it asked me to download the .sdx file associated with this version of windows. After the .sdx file is downloaded, I have the opportunity to "Launch" the .sdx file from a button on the dreamspark website, but this appears to initiate an upgrade of the OS instantly. I am simply looking to download a .iso from dreamspark, as it seems that using just any version of Win7 pro 64bit (tried the generic installation disc .iso) to bootcamp will tell me that I have provided an invalid product key (I know for sure this product key is valid). Any ideas on how I can retrieve a .iso from this .sdx file or where I can find a downloadable win7 pro dreamspark .iso?


How to get symbols for \thanks command with Thesis class

I'm having a slight problem with regards to the \thanks command.   My preamble is the following:  \documentclass[a4paper, 11pt, oneside]{Thesis}  % Use the "Thesis" style, based on the     ECS Thesis style by Steve Gunn \graphicspath{{Figures/}}  % Location of the graphics files (set up for graphics to be in PDF format)  % Include any extra LaTeX packages required \usepackage[square, numbers, comma, sort&compress]{natbib}  % Use the "Natbib" style for the references in the Bibliography \usepackage{verbatim}  % Needed for the "comment" environment to make LaTeX comments  \usepackage{vector}  % Allows "\bvec{}" and "\buvec{}" for "blackboard" style bold vectors in maths \usepackage{graphicx} \hypersetup{urlcolor=blue, colorlinks=true}  % Colours hyperlinks in blue, but this can be distracting if there are many links   In the author section I have the following:  \begin{minipage}{0.4\textwidth} \begin{flushleft} \large \emph{Author:}\\  John \textsc{Smith}  \thanks{Student at the University of Cape Town}  \end{flushleft}  \end{minipage}   ~  \begin{minipage}{0.4\textwidth}  \begin{flushright} \large   \emph{Supervisor:} \\   Dr. John \textsc{Doe\thanks{Lecturer at the University of Cape Town}} % Supervisor's Name \end{flushright} \end{minipage}\\[2cm]   I then get the following output    But I don't want the number, I want the symbols, like in the example here:


If I award a bounty can I raise another on the same question?

I have a bounty that is about to expire from its 24 hour grace period. None of the answers actually work.  has proved useful, in that I have learnt something useful from it, but  looks promising if the answerer follows up to address my comment. I am tempted to award the bounty to the first of these answers and then raise a second bounty on the same question but it is not clear to me from the  whether they can be awarded a second time on the same question.


NPE when using ThreadLocal + AtomicLong in Java

I'm initializing using public static ThreadLocal<AtomicLong> count = new ThreadLocal<>();  How do I use AtomicLong method for count? The below throws a NPE:  count.get().addAndGet(records.size());


How is ctrl + / working as undo in Zsh 5.7.1 on Debian 10.0?

I have a Debian 10.0 system. It has zsh 5.7.1 (x86_64-debian-linux-gnu). In ZSH prompt, I type foo bar baz  Then I type alt + backspace two times. The words baz and bar get deleted and only foo remains. Then I type ctrl + / two times to undo the deletions. The words baz and bar reappear. How is ctrl + / working as the undo command? I don't see it defined anywhere? $ echo / | grep -E "/|undo"  # just testing my regex / $ bindkey -l .safe command emacs isearch main vicmd viins viopp visual $ bindkey -M .safe | grep -E "/|undo" $ bindkey -M command | grep -E "/|undo" $ bindkey -M emacs | grep -E "/|undo"  "^X^U" undo "^Xu" undo "^_" undo  I also have a macOS Catalina 10.15.7 with zsh 5.7.1 (x86_64-apple-darwin19.0) and ctrl + / does not do anything there.


How to prove or disprove statements about sets

Prove or disprove:  The set: $\{ \emptyset\}^{\Bbb N}$ has only one element.  The set $\emptyset^{\Bbb N}$ is empty.    I'm pretty sure both are true, for 1. all the natural numbers go to the empty set and that is the only element. Where as 2. all the natural numbers go to nothing so that's why it's empty. (Same as $ {\Bbb N}^{\emptyset} $ nothing goes to something is nothing (I think)). The problem is I have no idea how to show this so advice would be appreciated.  Edit: My defintion of a function is: $f:B\to A$ if  $(a_1,b),(a_2,b)\in f \ \Rightarrow \ a_1=a_2$ So for 2. I can simply say that: $(1,\emptyset),(2,\emptyset)\in f \Rightarrow a_1\neq a_2$  ?


Byte array throwing a null pointer exception when the byte array is not null

I'm making a simple program that I'm trying to add multiplayer for. I currently have byte arrays (byte[]) for the data that's being sent to the server and to the clients. When I send a byte array after I move the player on the screen I get a java.lang.NullPointerException and I know that it is not null. I've even tried putting an if statement checking if it's null and eclipse said it was dead code.  if (data == null) {     System.out.println("Data is null!"); }   Here is my code where it gives me the exception.  byte[] data = new byte[10];  byte packet00 = (byte) ((byte) x/8); byte packet01 = (byte) ((byte) x/8); byte packet02 = (byte) ((byte) x/8); byte packet03 = (byte) ((byte) x/8); byte packet04 = (byte) ((byte) x/8); byte packet05 = (byte) ((byte) x/8); byte packet06 = (byte) ((byte) x/8); byte packet07 = (byte) ((byte) x/8);  byte type = 39;  data[0] = 2; data[1] = packet00; data[2] = packet01; data[3] = packet02; data[4] = packet03; data[5] = packet04; data[6] = packet05; data[7] = packet06; data[8] = packet07; data[9] = type;  client.sendData(data);   x is an int that is changed by a key press, and the method sendData from client takes a byte[].  I couldn't find anything to help me fix this, and I want to know if I'm missing something and/or a fix to this.  Here's a portion of the stacktrace:     Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException           at com.dripgames.main.Main$1.keyPressed(Main.java:132)           at java.awt.Component.processKeyEvent(Unknown Source)


I want to create a TeX document for which the first (summary) page is \documentclass[10pt]{article}, but for which the rest of the document is \documentclass[12pt]{article}. Is there an easy way to do this?


Why pgfplots sometimes cycles markers and colors and sometimes doesn't?

Why the following examples differ considering line color and markerstyles?  First one draws black lines with no markers. Same thing happens when I add plots with \addplot table [x index=0, y index=1]{data.dat} command.  \documentclass{article} \usepackage{pgfplots} \begin{document}   \begin{tikzpicture}   \begin{axis}   \addplot[   domain=-3e-3:3e-3,   samples=201,   ]   {100+exp(-x^2 / (2e-3^2)) / (1e-3 * sqrt(2*pi))};   \addplot[   domain=-3e-3:3e-3,   samples=201,   ]   {exp(-x^2 / (2e-3^2)) / (1e-3 * sqrt(2*pi))};   \end{axis}   \end{tikzpicture} \end{document}   While this one cycles colors and markers.  \documentclass{article} \usepackage{pgfplots} \begin{document} \begin{tikzpicture}     \begin{axis}     \addplot plot coordinates {         (7,     8.472)         (31,    3.044)         (111,   1.022)         (351,   3.303)     };     \addplot plot coordinates {         (9, 7.88)         (49,    3.24)         (209,   1.23)         (769,   4.45)     };     \addplot plot coordinates {         (11,    6.88)         (71,    3.17)         (351,   1.34)         (14,  5.33)     };     \end{axis} \end{tikzpicture} \end{document}   I get cycling effect when I add plots with \addplot+ but I don't get why these examples differ.  This problem came up when I tried to visualize my data from text file. The first column contains x-axis data and the following columns contain data for y-axis. Data sets have 100 - 10 000 rows and 3 - 100 columns. What would be the best way the set color and linestyle for different columns?


How do i make an object emit an object that is emitting objects?

How do i get an object to shoot out an object that is shooting out objects with the particle system.


i'm new to python, trying to write a little compositing and rendering addon. One of its fonction is to add a button with rendering a still and writing the render and all the file outputs renders in the render path (the f12 button of the regular GUI doesn't do that). So here's the operator looks like  #####################################################    # Add render still operator def renderstill (context):     bpy.context.scene.render.display_mode = 'WINDOW'     bpy.ops.render.render(write_still=True, use_viewport=True)   class RenderStill(bpy.types.Operator):     """Render Current Frame Still and write all Outputs\nWarning : Blender is going to freeze during the render"""     bl_idname = "render.still_files"     bl_label = "Render Current Frame Still"     bl_options = {'REGISTER', 'UNDO'}      def execute(self, context):         renderstill(context)         return {'FINISHED'}   #####################################################   This works pretty good, but it freezes the gui. Is there a way to make this acts like a regular f12 render on the gui ? with tile viewing, progression bar... ?  Thanks in advance !


How to recover data from a hard drive crash?

Last night my 500 GB Seagate hard drive was fine but this morning it suddenly started crashing, somehow I made it work after a chkdsk but 2 partitions show space is full now but it wasn't when the drive was fine. The 3rd partition one is also acting weird.   Whenever I try to open any drive, Windows asks to format it. My drive is still under warranty but I don't want to lose any data. How can I recover data from this crashed/crashing hard drive?   my OS is: windows xp sp3 Processor: Inter Pentium 4 3.0 GHz 1 GB RAM Already have 2 other hard drives  1 - 320 GB - OS drive - seagate 2 - 1 TB - western digital   UPDATE 1: when using Test Disk: it's showing some read errors  UPDATE 2: Now all the partitions are not showing up in my computer, but can see the hard drive in hardware manager, now what to do ?  Here are some screenshots:


After the therapy, eight children (43%) became able to crawl/move on their back.   Or should I use "on their backs"?   Singular because each child only has one back, or plural because we're dealing with eight backs?


No Preview in the Preview Sequencer View (just white on black)

I am a new user and I just installed Blender 2.76b on a Lenovo R500, OS Windows XP Pro. I intend to use it mostly for (short) video editing. I could load, hear audio, cut and animate video correctly, but the preview is in a white square on a black background.   When I initialize Blender, I got the following output:  "AL lib: <EE> ALCdsoundPLayback_reset: Unknown system speaker config:0x0 Warning! Using result of ChoosePixelFormat."   and at the start this alert:  "Your system does not use 3D hardware acceleration. Such system can cause stability problems in Blender and they are unsupported. This may cause by: * A missing or faulty graphics driver installation.   Blender needs a graphic card driver to work correctly. * Accessing Blender through a remote connession * Using Blender through a virtual machine"   Cases two and three are not mine. Do I need any special driver for my graphics card (ATI Mobility Radeaon HD 3400 Series) to use Blender? Does it have anything to do with seeing no preview?


Analysis of a jar falling with a fly inside

This is related to other questions that are similar, but it's somewhat different. I was discussing the following situation with my father, and we don't quite agree on the result.  The situation is this: you have a jar, closed, falling due to gravity with no air resistance. Inside the jar, full of air, there's a fly, falling with the jar, located at the bottom. While the jar is falling, the fly lifts and goes to the top of the jar. The question is: does the jar reach the ground after, before or at the same time as if the fly hadn't moved?  My father thinks that the answer is this: you take the jar+air+fly as your system. The only external force acting on the system is gravity, so the trajectory of the center of mass follows the trajectory imposed by a=-g; the fly moves "up" respect to the center of mass, so it gets higher. In order to have that the trajectory is not altered, that lifting of the center of mass must result on the system "accelerating" and hitting the ground EARLIER than if the fly hadn't moved.  Me, I think there's something fishy about that "acceleration" in order to keep the trajectory invariant, because it's caused, somehow, by internal forces.  What do you think?  Thanks.  PS: editing to add the "homework and exercises" tag. It's not homework I have, but the question can be thought as belonging there. Thanks.


Is chat.SE implementation freely available?

I quite like the chat which is used here on SE network. (I like several features, such as showing to which line you are answering, having possibility to edit typos in your message for some time after posting it, basic markdown etc.)  I was wondering whether chat was created by SE team. And I would like to know whether source code of the chat is public and whether SE-chat can be used on different websites.


Duplicate sources warning found while updating

I use Ubuntu 14.04 LTS. When I run,  sudo apt-get update   the terminal gives me,  Reading package lists... Done W: Duplicate sources.list entry http://dl.google.com/linux/chrome/deb/ stable/main amd64 Packages (/var/lib/apt/lists/dl.google.com_linux_chrome_deb_dists_stable_main_binary-amd64_Packages) W: Duplicate sources.list entry http://dl.google.com/linux/chrome/deb/ stable/main i386 Packages (/var/lib/apt/lists/dl.google.com_linux_chrome_deb_dists_stable_main_binary-i386_Packages) W: You may want to run apt-get update to correct these problems   How to resolve this.


I am searching for a word or phrase that describes reflected light, dancing light etc

I am trying to find a word or short phrase that conveys the idea of reflected light, dancing light, flickering light. It is for an artistic project to name an artwork piece I am constructing where light throws patterns and colours onto a wall or surface through transparent colored film.


What is the square root of a negative number?

For $ x^2+1=0 $ , can we say that: $ x=+i $ and $ x=-i $


Can a finite sum of square roots be an integer?

Can a sum of a finite number of square roots of integers be an integer? If yes can a sum of two square roots of integers be an integer?  The square roots need to be irrational.


Have been trying to install Gnuradio for several days and keep having trouble with qt4 not building/installing properly. Seemed to depend on a thing named 'unity-control-center' which claimed to be dependent on two libraries, both of which claimed to be up to date. This is what I got if I tried to install just qt4. Get exactly the same unmet dependencies if I try to install any qt4 app from the Software Center, FWIW.  ftoewe@ftoewe-Inspiron:~$ sudo apt-get install qt4-dev-tools libqt4-dev libqt4-core libqt4-gui Reading package lists... Done Building dependency tree        Reading state information... Done Some packages could not be installed. This may mean that you have requested an impossible situation or if you are using the unstable distribution that some required packages have not yet been created or been moved out of Incoming. The following information may help to resolve the situation:  The following packages have unmet dependencies:  unity-control-center : Depends: libcheese-gtk23 (>= 3.4.0) but it is not going to be installed                         Depends: libcheese7 (>= 3.0.1) but it is not going to be installed E: Error, pkgProblemResolver::Resolve generated breaks, this may be caused by held packages. ftoewe@ftoewe-Inspiron:~$   Asked for help a couple of days ago and got messed up trying to complete a suggestion.  So back trying again.  Thanks in advance.


Linker error with C++ function template instantiation (member function of template-instantiated class)

I have lots of existing C++ code with template classes that have implementations in the .cpp files. I want to add a template function to one such class. My problem is that I cannot make the compiler instantiate the function template.  I've created a stripped example demonstrating the problem. I want to add the member function convert(), with an own template parameter LenNew:  template <typename Number, int Len> class MyClass { public:     // the function I'm trying to add     template <int LenNew>     MyClass<Number, LenNew> convert();      // other methods I want to keep this way     void function(); // implemented in .cpp file  private:     Number n[Len]; };   In the existing setup, the .cpp file implements methods and instantiates the class template:  template <typename Number, int Len> void MyClass<Number, Len>::function() {     // implementation }  // instantiate template-class with specific template parameters template class MyClass<double, 1>;   So I added the implementation for my new member function, and tried to instantiate the template, which doesn't seem to work:  template <typename Number, int Len> template <int LenNew> MyClass<Number, LenNew> MyClass<Number, Len>::convert() {     // implement... }  // try instantiate template<> template<> MyClass<double, 2> MyClass<double, 1>::convert<2>();   It compiles fine, but I get an undefined reference when I try to use convert() from a different .cpp file:  main.cpp:(.text+0x1c): undefined reference to `MyClass<double, 2> MyClass<double, 1>::convert<2>()'   Here is a Gist with the demo program:   Sorry, there seem to be a lot of very similar questions, but I could still not grasp what is wrong.


Can I cast a spell as a reaction when a creature enters the reach of my quarterstaff if I have the Polearm Master and War Caster feats?

The  feat (PHB, p. 168) says:     While you are wielding a glaive, halberd, pike, quarterstaff or spear, other creatures provoke an opportunity attack from you when they enter the reach you have with that weapon.   The  feat (PHB, p. 170) says:     When a hostile creature's movement provokes an opportunity attack from you, you can use your reaction to cast a spell at the creature, rather than making an opportunity attack. The spell must have a casting time of 1 action and must target only that creature.   Assume that I'm a wizard, with both Polearm Master and War Caster, and I'm holding a  (it's a magic quarterstaff).  Can I cast a spell (with a casting time of 1 action) as a reaction when a creature enters my quarterstaff's reach, targeting only that creature?


Automatically generate differences from two latex sources

Say for a use case of incremental review, I want to show from a previous revision to an existing one what has changed in the PDF rendering. Is there an existing tool which can do this? I already version my latex sources through git, I simply want to generate a new file which indicates the changed elements in a highlight or different colour to quickly point to the changes for somebody reviewing.


At the moment I write macros without breaking them up, like so:  \NewDocumentCommand{\HC}{ o }{\IfNoValueTF{#1} {\emph{HC}\xspace}{\emph{HC}, p.#1\xspace}}   This obviously gets pretty hard to follow once things get longer. Examples on this site are always broken into separate lines, using % at the end of each line. I have never been sure what the rules are for how to do this effectively, or what the practice of arranging code in this way is. I feel that I am falling into a very bad habit by ignoring this. Is there a guide to this anywhere on this site or elsewhere, or is it just personal preference?


I want to show that     For all irrational numbers $a \in \mathbb{R}$ there exists an $Q \in \mathbb{N}$ such that $|a-\frac{p}{q}| \lt \frac{1}{qQ}$ for $p,q \in \mathbb{Z}$ and $1 \le q \le Q$.   My attempt:  Let $a \in [0,1)$ and $Q \in \mathbb{N}$. Divide $[0,1)$ in $Q$ disjunct subintervals $I_i := [\frac{i}{Q}, \frac{i+1}{Q})$ for $i \in \{0,1,\ldots, Q-1\}$. Consider the fractional parts $\{na\} \in [0,1)$ of the number $na$ for $n \in \{0,1,\ldots, Q\}$. Since there are in total $Q+1$ such fractional parts but only $Q$ subintervals, by the Pidgeonhole Principle there must be at least one subinterval that contain at least two fractional parts. Let such two fractional parts be $\{na\}, \{ma\} \in I_i$. Wlog let $m \lt n$. Then  $$|\{na\} - \{ma\}| \lt \frac{1}{Q}$$  since those two fractional parts are in the same $I_i$ which has a width of $\frac{1}{Q}$. By the definition of fractional parts  $$\{na\} - \{ma\} = na - \lfloor na \rfloor - (ma - \lfloor ma \rfloor) = na - ma - \lfloor na \rfloor + \lfloor ma \rfloor = aq - p$$  for $q := n-m$ and $p := \lfloor na \rfloor - \lfloor ma \rfloor$. Also $p,q \in \mathbb{N}$, because $m \lt n$. It follows then   $$|aq - p| \lt \frac{1}{Q} \iff |a - \frac{p}{q}| \lt \frac{1}{qQ}$$  If $a \ge 1$ then we can write $a = a' + k$ for some $a' \in [0,1)$ and $k \in \mathbb{N}$. Then with $p' = p+qk \in \mathbb{N}$  $$|a - \frac{p}{q}| = |a' + k - \frac{p}{q}| = |a' - \frac{p+qk}{q}| = |a' - \frac{p'}{q}| \lt \frac{1}{qQ}$$  by the first case.  If $a \lt 0$ then the rational number must be negative too, so let $p \in \mathbb{Z}$ and $p \le 0$. Then with $a' := -a \gt 0$ and $p' := -p \ge 0$  $$|a - \frac{p}{q}| = |-(a' - \frac{p'}{q})| = |a' - \frac{p'}{q}| \lt \frac{1}{qQ}$$  by the first case again.  My question:  Is my proof correct? Is there anything which could be done better?  I'm still not really sure about the dependencies. $Q$ is really $Q_a$ so so only dependend on $a$?! And is $p,q$ really $p_a,q_a$ only dependent on $a$ too or also on $Q$?  Could I instead take numbers $na$ for $n$ from another subset than $\{0,1,\ldots, Q\}$ provided it has the same cardinality?  How can I guarantee that $p' \in \mathbb{N}$ because $k$ could be a negative integer. Also I think the final argument I gave, why considering  $a \in [0,1)$ is sufficient, is not really the essence.


Unable to execute certain programs even as root

I am unable to execute certain programs in various folders even as root. The programs have the correct permissions on them. For example see below  [root@ODHI01VMA02 bin]# ls -la java* -rwxr-xr-x 1 root root 56056 May 10  2013 java -rwxr-xr-x 1 root root 16674 May 10  2013 java_vm -rwxr-xr-x 1 root root 56056 May 10  2013 javaw -rwxr-xr-x 1 root root 78842 May 10  2013 javaws   When I execute java I get the following error.   [root@ODHI01VMA02 bin]# ./java -version bash: ./java: Permission denied  [root@ODHI01VMA02 bin]# ldd java     not a dynamic executable   This one does not work,  [root@ODHI01VMA02 bin]# file java java: ELF 32-bit LSB executable, Intel 80386, version 1 (SYSV), dynamically linked (uses shared libs), for GNU/Linux 2.2.5, not stripped    This one does work,  # file java java: ELF 64-bit LSB executable, x86-64, version 1 (SYSV), dynamically linked (uses shared libs), for GNU/Linux 2.4.0, not stripped    This is not just with the above program, i just used it as an example. There are other programs on other drives that have the same issue. Also a lot of other programs work without any issues.  This is on RedHat 6.7. Any Linux Gurus please help.  Jagi


Are commas below correct, please?  In the solution, we except  From the beginning, we search for


Just a problem from my old lap - Dell Latitude D430 : 1.3 Ghz Core 2 Duo, 2GB Ram.   I installed Ubuntu 14.04 just last week , but it was very slow when i run any applications.   And I found that Xubuntu is much better performance than Ubuntu on old lap.  So i download Xubuntu 14.04 . will it better performance on my laptop ? or i have to download the older Xubuntu or using Lubuntu ?


Example of A, B, G such that A is a normal subgroup of B, B is a normal subgroup of G, but A is not a normal subgroup of G

I need a counterexample to the following statement: if A, B are subgroups of a group G, and A is a normal subgroup of B, B is a normal subgroup of G, then A is a normal subgroup of G. I've tried using groups such as $Z/nZ$ and $Z_n^{*}$, but neither seem to work. Thanks for your help.


Why do I require 15 reputation to just up-vote something?

I've been lurking Stack Overflow whenever I had a problem for at least the last 2+ years. More times than not, I find my solution (or cobble one together) before I get frustrated enough to have the innernets help me with my specific custom problem.  Many times, the only commentary I would be able to add would be "thanks!" which really only wastes bits and bandwidth.  I understand implementing measures to keep the bots and SEO kids out, but sometimes it's a PITA to start participating in a community.  If you couldn't extract my question from the above rant (or title), this might be a little more clear:  Why do I require 15 reps to just up-vote something?  I feel like it's kinda silly.  Additionally, I noticed the quote off to the left:     We prefer questions that can be answered, not just discussed.   yet I have looked around here and haven't been able to find any justifiable explanation.


I want to add a box in a tabularx table that would frame several cells vertically. There is this post that shows how to frame cells horizontally (), but I cannot figure out how to do to have the box extend over several rows. Here is what I would roughly like to get (but with a nice box):  Column 1 & Column 2 & Column 3                       +-----+ bla      & bla      & |bla  |                       |     | bla      & bla      & |bla  |                       +-----+   Any idea of how I could do that?  Edit: the solutions proposed below are very nice. But they are compatible with the tabular environment only, it seems, and not with tabularx and booktabs. Below is the code I have used. Does anyone have an idea of how to extend these solutions to the tabularx style? If not, then I will just rewrite all my tables using the simple tabular style.        \documentclass{article}    \usepackage{tabularx, booktabs}    \usepackage{tikz}    \usetikzlibrary{calc}     \newcommand{\tikzmark}[1]{\tikz[overlay,remember picture] \node (#1) {};}    \newcommand{\DrawBox}[1][]{%         \tikz[overlay,remember picture]{         \draw[black,#1]            ($(left)+(-0.5em,2.0ex)$) rectangle            ($(right)+(0.75em,-0.75ex)$);}           }     \begin{document}    \begin{table}[H]    \centering     \begin{tabularx}{0.3\textwidth}{Y*{4}{c}}         \toprule          & Masc  & Fem & Neut\\          \midrule  \cline{4-4}         Nom & hic & haec & \multicolumn{1}{|c|}{hoc} \\          Acc & hunc & hanc & \multicolumn{1}{|c|}{hoc} \\ \cline{4-4}         \bottomrule      \end{tabularx}     \end{table}      \begin{table}[H]    \centering     \begin{tabularx}{0.3\textwidth}{Y*{4}{c}}         \toprule          & Masc  & Fem & Neut\\          \midrule           Nom & hic & haec & \tikzmark{left}hoc \\          Acc & hunc & hanc & hoc\tikzmark{right} \\          \bottomrule      \end{tabularx}       \end{table}     \end{document}


Crash course in classical thermodynamics

I've been working on some projects lately where it would be very handy to know more about thermodynamics than I do, but sadly I never had a chance to take a proper thermodynamics course in college. Unfortunately, right now I don't have the time to work through a 500-600 page undergraduate text on the subject.  Can anyone recommend a book/online resource/PDF that perhaps gives a (calculus based) broad overview of classical thermodynamics, say in something less than 200 pages?


If $(X,d)$ is a metric space, prove that intersection of any collection of compact sets in $(X,d)$ is compact.

If $(X,d)$ be a compact metric space then, arbitrary intersection of compact subsets is compact.  Is it true if $(X,d)$ is a metric space, but not compact?  There is similar type of questions already have been asked before, but those are from real-analysis where any closed and bounded set is compact. But in metric space closed and bounded set may not be compact. Hence this question is different from previously asked questions.


Does standard English include non-trivial sentences which admit no verb?

One of the interesting aspects of the Maori language, as I understand it, is that it includes a class of sentences which not only have no verb, it is positively wrong to form them with a verb.  Does standard English include any non-trivial sentences which have no verb, and are not simply ellipses of sentences which do include a verb?  African-American Vernacular English includes sentences like, "Where you at?", that have no verb. The corresponding sentence, "Where are you at?", doesn't sound like African American Vernacular English. Adding the verb "are" seems to transform it into White American English.  Phrases like, "Hey!" are interjections, and don't meet my threshold of being non-trivial. Answers like "Tomorrow." to "When will you file your story?" seem to be ellipses; in this case, of the verb-laden "I will file my story tomorrow."  I found a related question here in in EL&U, . The title notwithstanding, the question actually seemed to be asking for an explanation why a certain phrase was in fact not grammatical.  I realise that "standard English" is a bit of a contradiction. Sorry. I refer to any of the mainstream English language dialects, steering clear of pidgins and creoles, where no doubt lurk all manner of interesting grammatical structures.


Example 1) Let's say I have some random creature with protection from white, and my opponent plays , a white card with the effect "Destroy all creatures." Can my creature with protection from white be destroyed by a white card that isn't actually targeting it specifically?  Example 2) I was playing a match with a friend where I had  on the field against his 3 zombies. Is he able to declare his zombies as blockers even though Elite Inquisitor has "protection" from zombies?  If he can declare them as blockers, does protection mean that no damage is dealt by the zombies to  Elite Inquisitor?


debian for truecrypt-7.1a for ubuntu 14.04

I am unable to find debian package for truecrypt-7.1a version. Any idea where should i look for this debian? Please share if you have source code of truecrypt and steps for creating debian package for same.


Extract data points from moving average?

Is it possible to extract data points from moving average data?  In other words, if a set of data only has simple moving averages of the previous 30 points, is it possible to extract the original data points?  If so, how?


How do I effectively defeat the Wall of Flesh?

I've been having trouble defeating this monster. Even with lots of buff potions, health potions, high tier armor (Molten), and ranged weapons with plenty of ammo (Minishark), I can't seem to kill this boss.  Worse, when I get it down to about 2000 hp, even if I'm fairly far away, it'll suck me in and continually rise towards the skybox, which doesn't allow me to do anything for some reason.  How do I defeat the Wall of Flesh? What gear should I be using and what kind of potions do I need?


On one of my sites, I have over 600 Profile 2 profile types (most of them have between 20-30 field instances, some have additional fields just used in that one type). I've tested a few different methods for bulk deletion, but can't find a way using the Entity/Profile APIs to get the deletion to occur without basically wiping out the site for a few hours.  It seems that, when a content type, profile type, etc. is deleted, a ton of caches are cleared and rebuilt for each deletion, meaning the process goes something like:   Delete the entity type. (I do this part.) All the attached field instances are deleted. All the attached fields that have no other instances are deleted. All the field info and entity caches are cleared. All the caches are rebuilt (due to other visitors on the site trying to load pages which need those caches). Ready to delete another entity type.   Is there any quicker way of mass-deleting entity types (I've already removed all the entities themselves—they're quite simple and fast to remove)? I'd like to cut out steps 4 and 5, which take about 90 seconds.  (I changed to a different system for storing profiles, because the cache rebuild and memory requirements were getting out of hand with over 500 profile types (in addition to 20 other content types), and over 10,000 field instances!)


What is the purpose of -e in sed command?

I can't find any documentation about the sed -e switch, for simple replace, do I need it?  e.g.  sed 's/foo/bar/'   VS  sed -e 's/foo/bar/'


Behavior of ANSI escape codes when mixing background and foreground

I'm investigating once more my ANSI escape rendering scripts and I've found weird behavior. The output color is defined by background or foreground by both mixed together. Example: echo -e "\x1b[1;30;47m█████▀\x1b[0m" # or printf "\33[1;30;47m█████▀\33[0m\n"  it's a light gray and darker gray, even that the ANSI codes are bold black and white. If I remove white (47) I get black foreground, so it's kind of blending two colors 30 and 47 together. First of all, am I right, is this some kind of blending of colors? Is this behavior some kind of documented and explained in detail and every possible color how to blend two colors? Does it happen for all colors or only black & white? The reason why this is maybe the case is that I have a perfectly fine script for generating ANSI artwork but it's somehow broken for white or gray colors. The code is created based on Wikipedia articles, other similar resources, and also answers on this Q&A that help a lot. EDIT: This is not duplicate, I'm asking about behavior that colors and background mixing have 3 states, one both (BG and FG) apply or either one applies. I'm asking if this is documented somewhere because it seems that this is how ANSI Artwork is rendered. An example is this one:  That renders fine in XFCe terminal but fails to render properly in my code.


I need to work with Open Type Fonts only, as it is mandatory by my company. I used Open Sans, which is google font, and even though it says it's an Open Type font, when you click on the additional info, it says it is True Type Flavored? What does that mean?


Is there a contradiction with the frictional force acting on a rolling wheel on a flat surface, if you consider both the net force and the torque?

I have had a physics problem on my mind for a few days and it seems relatively simple at first, but it has been puzzling me, and I was wondering if you could help.  Say a student rolls a tire on a flat level surface. There is no car involved or anything it’s just the tire. As the tire rolls, the tire slows down by friction and eventually comes to a stop. I have drawn an extended free body diagram below in paint.    I have the wheel rolling to the right and gradually slowing down with acceleration to the left. Since it is accelerating to the left, then that means static friction must be pointing to the left. So this is the problem: If static friction is pointing to the left, that means friction is also creating a torque on the wheel that points into the screen. If there is a torque pointing into the screen that torque should speed up the wheel’s rotation! But that doesn’t happen. So the question is: How can we use just Newtonian physics (not energy considerations) to account for the fact that the friction force is doing two seemingly contradictory things at once? It’s slowing the wheel down by pointing to the left, but also speeding the wheel up by applying a torque into the screen. I’ve been struggling with this for a few days. I was thinking maybe I’m missing a force, like air resistance. But that shouldn’t matter. We should be able to perform this same experiment in a vacuum. Somehow, there must be some torque applied out of the screen to cause the wheel to slow in its rotations. But I don’t know how.


Why did the Hulk suddenly fight on the same side with the others?

Bruce Banner has no power over the Hulk. Bruce doesn't even remember what happens when he is the Hulk. He is afraid to turn into the Hulk all the time. Especially inside a Helicarrier. In one of the scenes, he crushed everything on his way and almost kill Black Widow, and fought with Thor.  But in the battle against the Chitauri in New York Bruce arrived on a small motorbike, did a maneuver and turned into the Hulk, who could understand where is the allies are and where is the villains.   I don't think that Bruce had learned to control him, because in Thor Ragnarok he didn't know that he spent 2 years on Sakaar.  So, why and how he could understand the situation?


Recently, I have found this problem:      Let $Q(n)$ denote the sum of the digits of a positive integer $n$. Prove that:  $$Q(Q(Q(2005^{2005})))=7$$   This topic is related to other two question I have asked:  and .   I have tried to solve this problem in many different ways, for example using the formula: $$Q(n)= n - 9 \sum_{k=1}^{\lfloor\log_{10} n\rfloor}\left\lfloor\frac{n}{10^k}\right\rfloor$$ but I'm stuck when I have to compute: $$Q(2005^{2005} - 9 \sum_{k=1}^{\lfloor\log_{10} 2005^{2005}\rfloor}\left\lfloor\frac{2005^{2005}}{10^k}\right\rfloor)= 2005^{2005} - 9 \sum_{k=1}^{\lfloor\log_{10} 2005^{2005}\rfloor}\left\lfloor\frac{2005^{2005}}{10^k}\right\rfloor- 9 \sum_{k=1}^{\lfloor\log_{10} \left ( 2005^{2005} - 9 \sum_{k=1}^{\lfloor\log_{10} 2005^{2005}\rfloor}\left\lfloor\frac{2005^{2005}}{10^k}\right\rfloor \right )\rfloor}\left\lfloor\frac{2005^{2005} - 9 \sum_{k=1}^{\lfloor\log_{10} 2005^{2005}\rfloor}\left\lfloor\frac{2005^{2005}}{10^k}\right\rfloor}{10^k}\right\rfloor$$   Or in other words, letting: $\Upsilon =2005^{2005} - 9 \sum_{k=1}^{\lfloor\log_{10} 2005^{2005}\rfloor}\left\lfloor\frac{2005^{2005}}{10^k}\right\rfloor $: $$Q(\Upsilon)=\Upsilon-9 \sum_{k=1}^{\lfloor\log_{10} \Upsilon\rfloor}\left\lfloor\frac{\Upsilon}{10^k}\right\rfloor$$  I have tried also using infinite sum, like complex Fourier series (see also this post ), but I don't know how to pass from an infinite series to the effective result.


Split a list of dictionaries into multiple lists of dictionaries in python

I have a list of dictionaries having 16k dictionaries. I want to split the list of dictionaries into multiple lists of dictionaries.  Current list of dictionaries -  list = [{'system_name': 'W1PVTL1098', 'fdc_inv_sa_team': 'X3Virtualization'},         {'system_name': 'W1PVTL1100', 'fdc_inv_sa_team': 'X3Virtualization'},         {'system_name': 'r3bvap1154', 'fdc_inv_sa_team': 'X2Linux_NSS'},          {'system_name': 'r1qvap1281', 'fdc_inv_sa_team': 'X2Linux_NSS'},          {'system_name': 'R3QVAP1123', 'fdc_inv_sa_team': 'X2Linux_GBS'},          {'system_name': 'W3BVAP1294', 'fdc_inv_sa_team': 'X2Windows_NSS'}]   Desired Output -  list1 = [{'system_name': 'W1PVTL1098', 'fdc_inv_sa_team': 'X3Virtualization'},          {'system_name': 'W1PVTL1100', 'fdc_inv_sa_team': 'X3Virtualization'},          {'system_name': 'r3bvap1154', 'fdc_inv_sa_team': 'X2Linux_NSS'}]  list2 = [{'system_name': 'r1qvap1281', 'fdc_inv_sa_team': 'X2Linux_NSS'},           {'system_name': 'R3QVAP1123', 'fdc_inv_sa_team': 'X2Linux_GBS'},           {'system_name': 'W3BVAP1294', 'fdc_inv_sa_team': 'X2Windows_NSS'}]


I am trying to run the following command in my system after navigating to the directory cd /etc/apt   Clean update: cd /etc/apt #out put stella@stella-box:/etc/apt$  sudo mv sources.list sources.list.ok   #output mv: cannot stat ‘sources.list’: No such file or directory  #Recreate sources.list and add these 4 lines to it. deb mirror://mirrors.ubuntu.com/mirrors.txt xenial main restricted  universe multiverse  deb mirror://mirrors.ubuntu.com/mirrors.txt xenial-updates main  restricted universe multiverse  deb mirror://mirrors.ubuntu.com/mirrors.txt xenial-backports main  restricted universe multiverse  deb mirror://mirrors.ubuntu.com/mirrors.txt xenial-security main  restricted universe multiverse    sudo apt-get clean  sudo apt-get update sudo apt install python3-pip sudo apt-get install cmake     I enter the next line it returns " mv: cannot stat ‘sources.list’: No such file or directory" please guys how do I fixed this error?


What are "good men that do nothing" called?

"The only thing necessary for the triumph of evil is for good men to do nothing." -Edmund Burke  Is there an idiom, phrase or preferably a single word that we can call people that could have helped but didn't? Bystanders don't necessarily have help to give. Cowards aren't particularly helpful either.    Addendum:  For example, once EMS has arrived on scene, bystanders are encouraged not to try to help, unless they're a nurse and therefore have the necessary skills to, and sometimes even then so. If in The Service, I would not want a coward (a liability) next me holding the line. Not to take anything away from these great answers, or to insist on a non-militaristic point of view, I would like to veer into the commercial or civilian realm in which I find this quote most often alluded to, E.G., "If we all gave 5 cents we could cure cancer tomorrow." Pretend most of us did give 5 cents and we did cure cancer, but you didn't give. You are now a(n) ____?... yes, I know what we call them, but what is their proper designation?


How do you compute negative numbers to fractional powers?

My teachers have gone over rules for dealing with fractional exponents. I was just wondering how someone would compute say: $$(-5)^{2/3}$$ I have tried a couple ways to simplify this and I am not sure if the number stays negative or turns into a positive. I know that if a negative number is raised to an odd power it is negative, but fractional powers are neither odd or even. Is there a general rule for dealing with these types of problems?


Invert screen colors on Android 4.4. KitKat

In Android Kitkat 4.4, is there a way to invert screen colors, that is make all colors negative? One would assume this would be a basic accessibility feature in today's world.


Do i have to update the serialVersionUID for this change?

If i change this method:  public void setCustom(Map<String, Object> custom) {     this.custom = (LinkedHashMap<String, Object>)custom; }   to:  public void setCustom(LinkedHashMap<String, Object> custom) {     this.custom = custom; }   do i have to update the serialVersionUID? Is it a compatible change or not?


how many integers $n$ have the property that there exist positive integers $a,b,c$ such that $a^n+b^ n=c^n$?

I want to know how to solve this question. I found this question in an online test but was not able to find the answer. Later after the test, when I reviewed the test, it showed the answer as $4$ but I want to know how the answer ends up in $4$. I tried a lot but wasn’t able to find the answer. Keep in mind that I’m a beginner and $a,b$ and $c$ belong to $Z^+$ and $n$ belongs to $Z$ Thanks in Advance


How to decrypt a text which is ciphered same length key?

I have ten piece of ciphered texts. I know that they ciphered with a same-length key. Any idea how I can decrypt the ciphertexts? What kind of algorithms should I use? What are the points of taking care of 'XORing' these texts with each other and space character? (text ciphered with the asymmetric key) should we use the frequency analysis?


support time of other Ubuntu LTS flavours?

I have read this  from  .It says that other Ubuntu flavors of LTS get only 3 years of support. Is this true?   This question is not a duplicate of the linked post as I want to know support time for only other Ubuntu flavors.


A limit of the p-th power of a function integral

What is $$\lim_{p\to0}\left(\int_0^1\left(f(x)^p\right)dx\right)^{1/p}$$  ?  Where f is continuous  It was an exam question and I don't know how to even get started with it, could you help? (It is not $f(x^p) $ but $\left(f(x)^p\right)$ so the p-th power of $f(x)$ )


ArcGIS automatically convert string variables to numeric?

If arcgis is automatically coverting string values to numeric variables in a text document generated by stata, how do you change those variables back into string? I tried opening up the fields under properties in arccatalog and it says I cannot change them because the tables are not empty


Yesterday, after some problems, finally I could install Ubuntu Server 14.04.2 and gnome GUI. Then I close the server. This morning, when I open it again it stops in this line: AH00558: apache2: Could not reliably determine the server's fully qualified domain name, using 127.0.1.1 set the 'ServerName' directive globally to suppress this message.  I've been looking for in Google, there are a lot of solutions, but no one works for me. Sure, because I'm new and there are a lot of things I don't know, but can somebody tell me how can I fix this problem? Please, step by step, I've tried to restart using recovery mode - root, but all commands fails.


How much electric charge do electromagnetic waves carry?

Since electromagnetic waves have both electric and magnetic field components, which oscillate in phase perpendicular to each other and perpendicular to the direction of energy propagation. How much is that electric charge? Can you possibly get a shock in some way?


Difference between Expert at & expert in

I am expert in speaking English    Or     I am expert at speaking English   Which one is correct?


What model/make are this Freewheel and Freehub?

I am in the process of overhauling my old Motobécane racing bike and I'd like to replace the freewheel, if reasonable. However, there is no indication of who made it (the bike shop couldn't help) and I've never seen a hub like this online.  The Freewheel has a lock ring with splines on the outside and I'm wondering which tool to use to screw it tight on the hub.


Which is the best password hashing algorithm for PHP?

I was just reading a  to create a login system and while reading I saw about password hashing.  We are going to store an sha256 hash which is a string always containing 64 characters.  This article is teaching to use sha256 hash function. After reading this, I did not stop and started to search more about creating secure login system and then I came up with this article by . In this article, they are using sha512 hash function. This really confused me that which function am I going to use for my next login system. I still searched google for better article and found this article by . The writer recommends both sha256 and sha512.  Only cryptographic hash functions may be used to implement password hashing. Hash functions like SHA256, SHA512, RipeMD, and WHIRLPOOL are cryptographic hash functions.  I thought my search is over and I can use sha256 or sha512 function but while searching more I found this . The accepted answer by  had new things for me. The things about I have never heard before which is bcrypt and scrypt. All this stuff was written about 2 to 4 years ago. Question Which is the best password hashing algorithm used these days for PHP?


static function error LNK2001: unresolved external symbol "private: static int B::s_nValue"

#pragma once class B { private:   static int s_nValue;  public:   B();   ~B();    static int GetValue() { return s_nValue; }    static void SetValue(int value){ s_nValue = value; }  };  int _tmain(int argc, _TCHAR* argv[]) {   int i = 0;   B::SetValue(5);    std::cout << B::GetValue();    cin>> i;    return 0; }   I'm trying to master the use of static functions. In this case, SetValue() and GetValue() are defined in class B.   They are called without an object definition in main. This should work, but I'm getting an unresolved external symbol error 2001. The precompiled headers option is turned off.  How can I get rid of this error?  Using MS Visual Studio 2012


What does do_action() function do in wordpress?

In my wordpress project I have seen several times the use of do_action() function.   I don't know the working of this function, nor why we call it or where we use it?  Can someone please explain this to me?


Is there a way to specify a type in runtime through casting a string with the types name? I hop my non-compiling code below can explain what i am trying to do. Let me know otherwise and ill try to explain it better.  var valueFromDropDownMenu = "MyClass";  List<Type.GetType(valueFromDropDownMenu)> dynamicList =    new List<Type.GetType(valueFromDropDownMenu) > ();   // Code to iterate through objects and populate dynamicList  // with all objects of correct type   What I am trying to do is to let the user choose what type of object I will process.   I am Using Unity3D which is a game dev framework and it uses a static method to load resources from files. These resources needs to be cast.   I'm trying to make a developer tool that lets the developer choose a specific type of resources to be loaded. So i need to do something like   var files = LoadAll("Path, ofType(UserSelectedType));    Is it possible?


What's my health situation like living in an exposed fiberglass insulation for 2 weeks

My attic floor is covered with fiberglass insulation. I go to the attic very often. Sorting out winter/summer clothes. Or I go up to search for stuff as my attic is a short term storage.   2 weeks ago, we had water damage up in the attic which softened the floor and the ceiling of my son's room. A quarter of the ceiling collapsed and exposed some of fiberglass insulation. To dry up the wetness, windows were opened all the time. I am worried that particles of the fiberglass are all spread out throughout the house, through the ventilation, and my family may have been inhaling it for too long (2 weeks).   My hubby had a severe nose bleed the other day which required him to seek urgent help. At the hospital, they found out his big vein had burst. The bleeding only stopped after his nose was cultured . Now I wonder if we have all accumulated a handful of fiberglass in our lungs.  In particular I'm worried about my son's health in particular as he's only 14 years old. I have been having some pinching-like discomfort in my chest down to my abdomen and funny feeling in my mouth; a burning sensation.  I do not know if we should be at home while the ceiling will be ripped off... is it risky?  Insurance is carrying out the repairs.  Anything else I have to be aware off?


Best way to optimise an if statement in C#?

I was writing an app, and for this piece of code(in the end of a method)  if (selectSdfDialog.ShowDialog() == DialogResult.OK) {     Sdf = selectSdfDialog.FileName;     var regex = new Regex("[VQ]\\d{11}");     Serial = regex.Match(selectSdfDialog.SafeFileName).ToString(); }   Resharper gave me a hint to invert the if statement, bringing it to this  if (selectSdfDialog.ShowDialog() != DialogResult.OK) return; Sdf = selectSdfDialog.FileName; var regex = new Regex("[VQ]\\d{11}"); Serial = regex.Match(selectSdfDialog.SafeFileName).ToString();   My question is, is this working faster or somehow better, and if yes, what is the difference for the compiler?


Prove that a function which is analytic in the whole plane and satisfies the inequality $|f(z)|<|z|^n$ for some $n$ and all sufficiently large $|z|$ reduces to a polynomial.   The function is analytic, so $f^{n}(z)$ exists for all $n$, all $z$. We have the Cauchy's integral formula for higher derivatives  $$f^{(n)}(a)=\frac{n!}{2\pi i}\int_C\frac{f(z)}{(z-a)^{n+1}}dz.$$  So $$\int_C\frac{f(z)}{(z-a)^{n+1}}dz<|z|^n$$ for all large $|z|$. How does that help?


Should Savage World Allies be made as Wild Cards?

I've been reading the basic manual on Allies and Extras, and it seems it's intended for such characters to work as non-wild card characters.  I'm playing a Super Powers game with friends, and they will be meeting other "supers" in the way and befriending them, however I'm left wondering if such allies are meant to be crafted as WCs, since there are even edges dedicated to giving the PCs Wild Cards as allies instead of Extras, making me think I might be doing something game breaking.


Here I faced challenge for fixing line number style as like the attached image could any one help how to fix this.  Note: Required style as indicated in green color    MWE  \documentclass{book} \usepackage{multicol} \begin{document} \section{Overview} Numerous videos  and interactivities are embedded just  where you need them, at the point of   \subsection{Links with our times} When a new suburb is established today, roads and footpaths are built, services such as water and electricity are connected, and underground  pipes are installed to take away sewage and  stormwater. All these facilities are  usually in place before any homes are built,  and even the construction of the  houses is governed by strict building regulations.  The situation was very  different two hundred years ago.  \begin{multicols}{2} As we learned in topic 2, the population increased dramatically in  Britain during the Industrial Revolution. Changes in agricultural  practices,  as well as job opportunities in the  newly established factories, brought  large numbers of people into rapidly growing towns and cities. This  influx of people was not matched by the provision  of the types of server   As we learned in topic 2, the population increased dramatically in  Britain during the Industrial Revolution. Changes in agricultural     practices, as well as job opportunities in the newly established  factories, brought large numbers of people into rapidly  growing towns and cities. This  influx of people was not matched by the provision  of the types of server  \end{multicols} \end{document}


Im learning at the moment c++ with a book. I have many problems with the pointers...   int i; cin >> i; const int *quantity = &i;  int array[*quantity];   Is that correct? Can i control now the size of the array during the programm is running?


How to find Origin for Angular Momentum?

I am studying angular momentum and I get the concept that it has a meaning or it is defined only with respect to a  certain point (often called as origin). I was looking at the realtionship between torque and angular momentum around an origin i.e.  net torque  = Rate of change of angular momentum (equation 11.29 in the picture). I think i get this relationship. Where I got confused when author adds a caution (full quote below) to the equation saying that:  If the center of mass of the system is not accelerating relative to an inertial frame, that origin can be any point.  However, if it is accelerating, then it must be the origin.  I am not sure if I get that statement and caution.  Not sure what the author means by the “origin” here.  Can't the origin be any point that we choose?   Let $\vec{\tau}_{\mathrm{net}}$ represent the net external torque, the vector sum of all external torques on all particles in the system.  Then we can write Eq. 11-28 as \begin{equation}   \vec{\tau}_{\mathrm{net}} = \frac{d \vec{L}} {dt} \qquad \text{(system of particles)} \tag{11-29} \end{equation} which is Newton's second law in angular form.  It says  The net external torque $\vec{\tau}_{\mathrm{net}}$ acting on a system of particles is equal to the time rate of change of the system's total angular momentum $\vec{L}$.  Eq. 11.29 is analogous to $\vec{F}_{\mathrm{net}} = d\vec{P}/dt$ (Eq. 9-27) but requires extra caution: Torques and the system's angular momentum must be measured relative to the same origin.  If the center of mass of the system is not accelerating relative to an inertial frame, that origin can be any point.  However, if it is accelerating, then it must be the origin.  For example, consider a wheel as the system of particles.  If it is rotating about an axis that is fixed relative to the ground, then the origin for applying Eq. 11-29 can be any point that is stationary relative to the ground. However, if it is rotating about an axis that is accelerating (such as when the wheel rolls down a ramp), then the origin can be only at its center of mass.


Does there exist any isomorphism between $\mathbb Q[\sqrt 2]$ and $\mathbb Q[\sqrt 3]$?

Does there exist any isomorphism between the fields $\mathbb Q[\sqrt 2]$ and $\mathbb Q[\sqrt 3]$ ?


Is there any software that for drawing graphs (edges and nodes) that gives detailed maths data such as degree of each node, density of the graph and that can help with shortest path problem and with algorithms such as Dijkstra ?  Thanks!


I commited my file and pushed to GitHub. But I forgot to add my HTML file. So I used git commit --amend to amend my commit. But now how can I resolve my mistake on GitHub?


Should I choose a postdoc with greater potential for collaboration over a higher ranked institution?

I'm in the market for math postdocs and was just offered some positions. Essentially my situation is as follows. I have two offers from AMS Group I universities. One has higher "ranking" and is in the top 15, and the other in the 30s. However, the lower ranked university has a great group and there is a greater potential for collaboration.  I'm concerned that if I go to a lower ranked place, faculty positions at a good institution will not be easy to find. How important is it to go to a famous university for you postdoc? I'd also like to hear about the experiences of mathematicians who didn't go to a top 10 university for the their postdoc, but worked their way up.


Given input as:  #start   random string 1 #end  #start   random string 2 #end   I can write a regex as   (#start[\s\S]*?#end)   Now thing gets a bit complex with this given data:    #start     random string 1     #start       random string 2     #end   #end    #start     random string 3   #end   and i want to get 03 matches, which are:  #start   random string 1 #end  #start   random string 2 #end  #start   random string 3 #end   Will this even be possible with regex? Cause i tried most of the regex rules, but i think i missed something cause it doesn't work as I want.  Can someone show me which rules can I used to achieve this goal?  Thank you.


How to test if n / 2 * 3 + n % 2 * 2 will overflow?

How can I rewrite this test so that the test itself won't overflow? Can I use the fact that (size_t) -1 is odd (power of 2 minus 1)?  size_t size; ... if ((size * 3U + 1U) / 2U > (size_t) -1) {     /* out of address space */ }   EDIT: Sorry, my question title was wrong. I don't want to check if (n * 3 + 1) / 2 will overflow, but if n / 2 * 3 + n % 2 * 2 will. I changed the title. Thanks for your correct replies to a bad question.


How to branch based on the documentclass?

I have a macros.tex file where I keep my macros and  I use them with different document classes.  I want to skip including some of my macros  based on the document class (e.g. if it is beamer). How can I branch based the document class?


I am producing some maps of a point layer using arcpy.mapping.ExportToPDF. Is there a possibility of creating HTML popup for the final PDF based on this link?


In Avengers: Infinity War, Thor gets Stormbreaker, and uses it to summon the Bifrost, bringing him, Rocket and Groot to Wakanda to fight Thanos' troops. But how did Thor know that they were in Wakanda, he didn't even know Wakanda existed, and Heimdall was dead so he couldn't direct him?


Why do planets in Star Wars only have one environment?

This thought came to me concerning the Star Wars universe.  On our planet (Earth) we have many different habitats (snowy wastelands, forests, cities); but in the Star Wars universe there only appears to be be one kind of environment per planet, e.g: Hoth is snowy, Endor is all forest and Coruscant is city.  Why is this?


I've always been an Ubuntu lover, but the only thing that holds me back from installing ubuntu on my laptop is iTunes. I have an iPad and an iPod touch and managing them without itunes is almost next to impossible, mainly because of ios upgrades.  Is there any way out?


How to use menu (Ubuntu dock) on right screen in 18.04?

I am using two screens. The menu (Ubuntu dock) is shown at the left screen. I would like to have it on the right screen:  Changing the right monitor as primary screen does not help. Only the top bar is now shown at the right monitor and on the left monitor is a gap between the menu at the top. Is it not possible to have the menu at the right in 18.04?


I have a HP Compaq p6-2469ea. And I am looking to add an Nvidia GTX 660 or better to run Grand Theft Auto V. Does anyone know if this possible?


So in the image below there are two circles, how can I remove the internal vertices between them without messing up the outside shape. I'm working on a gun and this is just a simple way to illustrate the issue I'm dealing with. If I where to go in and delete the internal faces it would leave holes on the outside of the object, is there a fast way to get around this?


regression with multiple response variable in R

How can I express multiple response variables for linear model?  For example, I can do this with single response variable   lm(Y1 ~ X1+X2+X3, data=somedata)   But if I want to use Y1-Y100 response variable in the model, how can I do that?  UPDATE: I am hasty. I just found an answer from   with(data, lm.fit(x=cbind(Intercept=1,x1,x2,x3), y=cbind(y1,y2,y3)))   and this one works too   lm(cbind(Y1,Y2,Y3) ~ X1+X2+X3, data=somedata)


If somebody clicks on up-vote or down-vote accidentaly, what is the way to undo it? or shoudn't it ask for confirmation?


I would like to move a file via the terminal using the mv command. The syntax is  mv file_old_dir file_new_dir  I am already in the directory where I want the file moved. I just did mv file_old_dir which didn't work.  How can I do this?  mv file_old_dir "here"


how to hide green pyramid of group objects handler

when I handle group objects, green pyramid disturb me. how can I hide these?


App Store is stuck in a loop trying to download a free app -- how do I make it stop?

My App Store keeps saying this item is free in the store, that this item will be added to your purchases and it then says cancel or download.   I click download and it won't download and keeps popping up the same message over and over again.  How do I make it stop? I can't download any apps.