### Animation using GNUPlot

Animation using GNUPlot I'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 dynamic curve - the 5 static curves correspond to the SDSS filter pass bands i.e the u,g,r,i,z band passes. And the dynamic curve is the composite quasar spectrum - which as i mentioned - will change with respect to the red shift of the quasar.
λobs=λem×(1+z)
is the relation between the emitted wavelength λem$\lambda_{em}$ and wavelength we perceive λobs$\lambda_{obs}$
As i said, i used gnuplot to create this gif and here's how to -
Create an animate.plt gnuplot script file.
# refer to http://gnuplot-surprising.blogspot.in/2011/09/creating-gif-animation-using-gnuplot.html in case any doubts pop up!
reset
set term gif animate
set output "animate10.gif"
# sets the terminal to give output in a gif format and save it as mentioned
n=50
# number of iterations
set xrange[500:10000]
set yrange[0:25]
# set xrange and y range - obviously
i=0
# obviously
plot "u.dat" u 1:($2*22) w l lc 000000 title "" replot "g.dat" u 1:($2*22) w l lc 000000 title ""
replot "r.dat" u 1:($2*22) w l lc 000000 title "" replot "i.dat" u 1:($2*22) w l lc 000000 title ""
replot "z.dat" u 1:($2*22) w l lc 000000 title "" # plot the filters in the first place. # lc 000000 is to draw the lines in black color. load "animate.gnuplot" # to load the data to be animated set output # to end animation sequence where the gnuplot.animate file contains the following replot "vandenberk_quasar_composite_spectrumtxt.txt" u ($1*(i*0.05+1)):(\$2) w l lc 000000 title ""
i = i+1
if (i<n) reread
and you can run this script in gnuplot as follows
gnuplot> load "animate.plt"
But i seriously suggest you run the commands one after the other dynamically on the gnuplot terminal - to check every step of the program.
Note -
gnuplot> load "animate.plt"
End of animation sequence
• If you don't see the End of animation sequence on the screen, then your animation is incomplete.
• If you see jibber-jabber on the screen after the command
gnuplot> load "animate.gnuplot"
then you haven't done
gnuplot> set output "output.gif"
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### on MOOCs.

For those of you who don't know, MOOC stands for Massively Open Online Course.

The internet is an awesome thing. It's making education free for all. Well, mostly free. But it's surprising at the width and depth of courses being offered online. And it looks like they are also having an impact on students, especially those from universities that are not top ranked. Students in all parts of the world can now get a first class education experience, thanks to courses offered by Stanford, MIT, Caltech, etc.

I'm talking about MOOCs because one of my new year resolutions is to take online courses, atleast 2 per semester (6 months). And I've chosen the following two courses on edX - Analyzing Big Data with Microsoft R Server and Data Science Essentials for now. I looked at courses on Coursera but I couldn't find any which was worthy and free. There are a lot more MOOC providers out there but let's start here. And I feel like the two courses are relevant to where I …