### you should start using git/github right now!

It's surprising to me that I haven't written about git on my blog so far! In fact, I have a small post on git on my github page so I guess I confused this with that. Either way, for lack of a better alternative, I am going to ramble about the practical use of git again! In fact, I've taken it upon myself, now and a number of times in the past, to convince my friends and those around me to use open source tools. From unix to latex, from git to ipython, I've acted as a small-time open source evangelist, so to say...

Coming to the point, git is a tool to keep track of the changes you make in a file. In fact, some of you might tell me that microsoft word has this functionality inbuilt i.e display the various corrections/additions made in a file at various points in the past. Well, yes, git isn't automatic and you will have to manually save (commit) the changes in a file. But git gives you the additional functionality that the files are available in a centralized server which anyone, with permission, can access and can make (push) changes to and download (pull) changes from. Okay, a different faction might now argue that google docs has this feature and multiple copies of the same file can be stored on individual machines and one can comment on each other's files. There are many such collaborative writing (publishing) tools available online, more so for latex. But what if you didn't want such a bulky interface and have access to a constant internet connection?

We can go on and on arguing about the pros and cons of git but you will never be convinced of whether or not it will fit into your routine until you try it. So without any more babble, let me give you the 4 important bits -

$git clone url # will download the contents of the git repository # and create a location (referred to as remote) for # the code to be pushed automatically. One can also use # git pull url # in which case the contents will be downloaded but # one will have to set the remote manually using # git remote add remote remoteurl$ git add *
$git commit -m 'foo bar' # will commit changes made to all of the files in a repository. # git commit -a -m 'foo bar' # can also be used if you want to *commit* all of # the changes from the previous version.$ git push remote
# to push the commit i.e the changes to the remote location.

I store all of my code in various repositories on github. Here's my github repository page.  Apart from all of the above mentioned commands, before one starts using github to store their code, one needs to authenticate their system with one's github account. Here's a github guide as to how to set that up.

I guess this adds to the many, many posts people have written on git and github. I just hope that this didn't dissuade you from using git even if it didn't persuade you to do so!

### Animation using GNUPlot

Animation using GNUPlotI've been trying to create an animation depicting a quasar spectrum moving across the 5 SDSS pass bands with respect to redshift. It is important to visualise what emission lines are moving in and out of bands to be able to understand the color-redshift plots and the changes in it.
I've tried doing this using the animate function in matplotlib, python but i wasn't able to make it work - meaning i worked on it for a couple of days and then i gave up, not having found solutions for my problems on the internet.
And then i came across this site, where the gunn-peterson trough and the lyman alpha forest have been depicted - in a beautiful manner. And this got me interested in using js and d3 to do the animations and make it dynamic - using sliders etc.
In the meanwhile, i thought i'd look up and see if there was a way to create animations in gnuplot and whoopdedoo, what do i find but nirvana!

In the image, you see 5 static curves and one dynam…