Is there any code to reverse the order of the column of a table?
How can I reverse (flip horizontal) a table?
My MacBook Pro has a flashing question mark in a folder against a grey background My MacBook Pro shows a grey screen with a flashing question mark in a folder. I tried connecting it to an older MacBook using firewire cable. I restarted the Macbook Pro in Target Mode. Now I see Thunderbolt and Firewire icons flashing and moving in a grey background. There is a green power icon at the bottom as well. I am not an expert even though I have been using Macs for ages.  How can I fix this issue so I can recover/backup things in the MacBook Pro hard drive? I know and have observed that the the division algorithm can be used to convert any number in the decimal system to the binary system. However, I have tried searching for an intuition of why this method works, and I just can't seem to see anything, although I know what type of intuition I am trying to make out.   So, my question is why we can use the division algorithm to convert between the decimal bases and any other number bases?   An example from the decimal system to binary would be appreciated. Intuitive explanation of why $\dim\operatorname{Im} T + \dim\operatorname{Ker} T = \dim V$ I'm having a hard time truly understanding the meaning of $\dim\operatorname{Im} T + \dim\operatorname{Ker} T = \dim V$ where $V$ is the domain of a linear transformation $T:V\to W$. I've used this equation several times in many problems, and I've gone over the proof and I believe that I fully understand it, but I don't understand the intuitive reasoning behind it. I'd appreciate an intuitive explanation of it.  Just to be clear, I do understand the equation itself, I am able to use it, and I know how to prove it; my question is what is the meaning of this equation from a linear algebra perspective. Why do electron and proton have the same but opposite electric charge? Polynomials with integer coefficients such that $p(a)=b,p(b)=c,p(c)=a$ While studying polynomials a question struck in my mind that  To have a polynomial $p(x)$ with integer coefficients and $a,b,c$ are three distinct integers, then is it possible to have $$p(a)=b$$$$p(b)=c$$$$p(c)=a$$ I have a 64-bit (amd64 a.k.a. x86_64) Debian or Ubuntu installation. I need to run 32-bit (i386/i686) programs occasionally, or to compile programs for a 32-bit system. How can I do this with a minimum of fuss?  Bonus: what if I want to run or test with an older or newer release of the distribution? I want every new user from now on to have bash as their shell by default.    I know that to change your own shell to bash, you would use the command "chsh -s /bin/bash", but how do I automatically set all future users' shell to bash by default? How do I check if an integer is even or odd? How can I check if a given number is even or odd in C? How do I add the kernel PPA? SSH to open GUI on target machine? network connection over thunderbolt bridge between linux and mac Smallest dense subset of $\mathbb{R}$ I am not sure if what I am looking for even makes sense (or) exists. Anyway I would be happy if someone can clear my confusion.  The set of real numbers $\mathbb{R}$ is obtained as completion of $\mathbb{Q}$. However, $\mathbb{Q}$ is not the only set which is dense in $\mathbb{R}$. $\mathbb{Q} \backslash \mathbb{Z}$ is also a dense subset of $\mathbb{R}$. I am wondering if it makes sense to talk of the "smallest" dense subset of $\mathbb{R}$. To phrase what I am looking for precisely and what I mean by smallest, I am looking for a dense set $A$ of $\mathbb{R}$ such that if $B$ is a proper subset of $A$ then $B$ is not dense in $\mathbb{R}$. I am able to "see" that the set $A$, I am looking for doesn't exist since any open interval consists of infinite rationals. But I am unable to precisely argue out to myself and convince why $A$ doesn't exist. Could some one throw more light on this? Am I able to change my GPA once I submit a graduate school application? How do I set read/write permissions my hard drives? Detecting pattern at the end of a line with grep I have 3 accounts that I am deleting - however, several hours after the 24 hour (+ grace period - end about 4-5 hours ago), the countdown completed, but disappeared and the accounts are still there.   I would rather not go through another 24 hours, and would like to have these accounts deleted (and yes, I have thought about it and this decision is not up for discussion).  Currently, the accounts are still there.  Could this please be seen to? I noticed that if I transfer a few large files between two hard drives, it's pretty speedy, at around at least 30&nbsp;MB per second, but if I transfer thousands of files less than 5&nbsp;KB, it is pretty damn too slow.. around 1 to 2&nbsp;MB per second.   Is there a way to speed up the copy/paste process with thousands of small files on Windows 7? I've got an MP4 video file and I want to add another AAC audio track to it. I've tried YAMB and MeGUI (frontends for MP4Box) and it plays correctly in Zoom Player, but it picks the wrong track in WMP and plays both at once in Quicktime. I think this might have to do with designating the default audio track somehow.  Does anyone know how to specify the default audio track with YAMB/MeGUI or know of another way of adding a track to an MP4 file? I hope this isn't a duplicate.  Similar questions that I found are over a year old.  I have seen cases where shortly after an upvote (perhaps on an old answer?), the summary in my user activity dropdown shows inconsistent counts:    Particularly, the Slid a div offscreen using jQuery answer shows +40, when it was only updated once yesterday.  Now, if this is a monthly total for this question, then it is correct, but when I refreshed later I got:    Now it shows +10, and other entries completely disappear.  So, what is this supposed to show me?  At the very least I am confused about what I am supposed to see here.  Here is another example:    This shows +20 for the same question as before, after I received a single upvote last night.  What gives?  You can see from my reputation that there was only a sinle upvote recently: This one is killing me, any help is greatly appreciated!