Gnuplot.py plotting multiple lines on the one graph

Question

I'm currently stuck trying to plot multiple lines from a text file using gnuplot py. I can get both lines plotting individually but when I try to plot both of them on the same graph, it only plots one line.

This is my code:

#!/usr/bin/env python   

import Gnuplot  

g = Gnuplot.Gnuplot()   


g('set terminal png') # Output of graph will be .png    
g('set output "' + "python_test.png" + '"') # Set the name of the output file    
g('set term png size 1200, 800')    
g('set lmargin 8')    
g('set rmargin 4')    
g('set tmargin 3')    
g('set bmargin 3')    
g('set xdata time')    
g('set timefmt "%H:%M:%S"')    
g('set format x "%H:%M:%S"')    
title = "Python Test graph "    
g('set title "' + title + '"')    
g('set xlabel "Time (HH:MM:SS)"')    
g('set ylabel "' + "quantity" + '"')
#g('set xrange [*:*]')

plot_cmd = "< head -n -1 "
datFile = "data.dat"

g('plot "' + plot_cmd + datFile + '" using 1:3' + ' title "' + "Line 1" +'" with lines')
g('plot "' + plot_cmd + datFile + '" using 1:5' + ' title "' + "Line 2" +'" with lines')

I've managed to get multiple lines plotted just using gnuplot plot but I can't seem to get it to work when I'm using gnuplot py which is what I need to use as I'm wanting to produce a gnuplot graph using my python script.

If needed, here is a link to my datFile: link

I'm not familiar with the gnuplot module but this appears to be creating two plots. For a single plot with two lines you issue just one "plot" command. — agentp
– agentp, Commented Sep 11, 2014 at 15:36
@george I've tried variations of that, for example, I tried g('"'datFile + '" using 1:5' + ' title "' + "Line 2" +'" with lines') but it says "invalid syntax" when I tried that. — Mark O'Sullivan
– Mark O'Sullivan, Commented Sep 11, 2014 at 15:40
try something like this : g('plot "' + plot_cmd + datFile + '" using 1:3 , "' + plot_cmd + datFile + '" using 1:5') (note the comma separating the two lines ) — agentp
– agentp, Commented Sep 11, 2014 at 15:54
@george it kind of worked but there was no lines, I had to add this to get it to work correctly: g('plot "' + plot_cmd + datFile + '" using 1:3 with lines, "' + plot_cmd + datFile + '" using 1:5 with lines') . Do you want to add your answer and then I can accept it as the answer? Also do you think it's possible to get it to work on separate lines like I had in my original code or will I have to keep it the way it is? — Mark O'Sullivan
– Mark O'Sullivan, Commented Sep 11, 2014 at 16:12
glad it works, feel free to write up an answer and accept - I don't want to post an answer since it was basically a guess and I cant test it myself. — agentp
– agentp, Commented Sep 11, 2014 at 17:13

Mark O'Sullivan · Accepted Answer · 2014-09-12 22:18:51Z

1

In order to get it working, I had to merge these two lines of code into one line of code.

g('plot "' + plot_cmd + datFile + '" using 1:3' + ' title "' + "Line 1" +'" with lines')
g('plot "' + plot_cmd + datFile + '" using 1:5' + ' title "' + "Line 2" +'" with lines')

This is the code which allowed me to plot multiple lines:

g('plot "' + plot_cmd + datFile + '" using 1:3 with lines, "' + plot_cmd + datFile + '" using 1:5 with lines')

Big thanks to george who helped me find a solution to my problem!

answered Sep 12, 2014 at 22:18

Mark O'Sullivan

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