plot multiple curves with color based on a color map in GNUPLOT

Question

Here is the problem I am having with GNUPLOT: I have data files with two columns each (one for the voltage the other for the current) and each obtained for a certain temperature (which is specified in their name something like iv_300K.dat, iv_290K.dat etc.).

Now what I want is to plot each data file on the same graph and each plot to have a colour based on the file name (I would like to show you a figure I made with Mathematica but it seems that my reputation is too low...)

So lets say I have iv_300K.dat, iv_250K.dat and iv_160K.dat I would like to have three curves coloured first red, second green-ish and third blue, but based on the temperature information in the file name.

I am thinking something similar to what I did in Mathematica:

ColorData["DarkRainbow"][Rescale[T, {160, 350}]]

Where "DarkRainbow" is a colormap and Rescale[x,{min,max}] gives x rescaled to run from 0 to 1 over the range min to max (according the Mathematica documentation).

So Rescale[250,{160,350}] = 0.473684

At the moment in GNUPLOT I am using the following for testing purposes:

plot for [i=350:160:-10] 'iv_'.i.'.K.dat' using 1:2 with lines title sprintf("".i." K")

but I can't get the colours to map the temperature.

Any help is appreciated!

Christoph · Accepted Answer · 2015-07-03 04:33:10Z

1

Use linecolor palette frac to select a color from a palette based on an value in the range [0:1]:

set cbrange [160:350]
set style data lines
plot for [i=350:160:-10] 'iv_'.i.'.K.dat' using 1:2 linecolor palette frac (i-160.0)/(350.0-160.0) title sprintf("%dK", i)

edited Jul 3, 2015 at 4:33

answered Jul 2, 2015 at 22:11

Christoph

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9 Comments

lucian Over a year ago

Thank you for your suggestion. I have just tried it but unfortunately I am getting the following error: Not enough columns for variable color. I have no idea where this is coming from.

lucian Over a year ago

I got it! it should be frac instead of frace! It works! Sweet! Now I don't mean to seem ungrateful but how can I change the color scheme to go from blue to red?

lucian Over a year ago

Got this as well! I found this resource here: github.com/Gnuplotting/gnuplot-palettes and I copy and pasted the description of the palette I wanted (jet in this case) at the beginning of my script and it works!

lucian Over a year ago

I have one more question: how can I add the unit next to the numbers in the legend on the right? I want to have it displayed something like 340 K, 250 K etc

Christoph Over a year ago

That is already contained in my answer: title sprintf("%d K", i)

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