Generating plots in Gnuplot using loops

Question

I would like to generate several plots using Gnuplot thats why I need to use loop. The data is loading from files "sort'i'.dat". The code is shown below but it doesn't work. I have got some problem with main loop. I don't know why it doesn't work, maybe it is connected with my version of Gnuplot. Thanks.

do for [i=0:10] {
  set term png
  set output 'sort'.i.'.png'
  set title "Quick sort"
  set xlabel "Position number"              
  set ylabel "Number on position"
  unset key                               
  plot 'sort'.i.'.dat' using 1:2 with points pt 5
}

The error is: "line 1: invalid complex constant"

Community · Accepted Answer · 2017-05-23 12:00:59Z

7

This kind of do for iteration was introduced in version 4.6.0:

The following iteration works only since 4.6.0:

do for [i=0:10] { print i }

The iteration

plot for [i=0:10] i*x

works also with 4.4

One other option for 4.4, although quite ugly, would be to "outsource" the iterations. Only two of the lines depend on the iteration variable, which make this feasible. You construct all the plot instructions outside of gnuplot and then eval the complete string:

As an example using bash:

set terminal pngcairo
set title "Quick sort"
set xlabel "Position number"              
set ylabel "Number on position"
unset key
set style data points

loopstr = 'set output ''sort%d.png''; plot ''sort%d.dat'' using 1:2 pt 5; '
eval(system('exec bash -c "for ((a=0;a<=10;a++)) do printf \"'.loopstr.'\" \$a \$a; done" '))

For the exec bash see gnuplot and bash process substitution. Of course you can use any other program to do the iteration.

But this doesn't of course replace the ease of having the gnuplot-internal iterations. Why not upgrade to 4.6?

edited May 23, 2017 at 12:00

CommunityBot

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answered Jan 22, 2014 at 9:13

Christoph

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6 Comments

user1519221 Over a year ago

Ok but this "plot for [i=0:10] ix" works only for one line but I need it for two lines for the same "i" for: "plot for [i=0:10] ix" and for: "plot 'sort'.i.'.dat' using 1:2 with points pt 5"

Christoph Over a year ago

The point was to show, that you need at least version 4.6.0. Which version do you have?

user1519221 Over a year ago

I have got 4.4 version.

Christoph Over a year ago

... and thats the reason why your do for iteration is not working, because for this you need 4.6

user1519221 Over a year ago

I know that but how to do something similar to this in Gnuplot 4.4.

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Hariom Singh · Accepted Answer · 2017-08-12 05:55:37Z

0

I had the same problem, and definitely the version of gnuplot is the issue. For example, I was working on gnuplot 1.8.10.0 and I got a message that I showed in the image 1. Then, I installed gnuplot 5.0, and it worked excellent! :).

gnuplot sample 1

gnuplot sample 2

All the best

edited Aug 12, 2017 at 5:55

Hariom Singh

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answered Aug 11, 2017 at 21:34

yovitza romero

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