pipe plot data to gnuplot script

Question

I want to create a gnuplot with three plots in it. The data should be inline (as I want to only

It should look like this:

Currently I am using the following gnuplot script to create the plot:

set terminal png
set output "test.png"
plot for[col=2:4] "data.txt" using 1:col title columnheader(col) with lines

The file data.txt is:

Generation Best Worst Average
0 2 1 0
1 3 1 2
2 4 3 3
3 4 3 3
4 6 3 4
5 7 4 5
6 9 6 7
7 10 6 9
8 10 5 6
9 11 6 8
10 12 7 9

I would like to pipe the data.txt into gnuplot and not to rely on the referenced data file in the script. Something like cat data.txt | gnuplot plot.gnu. The reason for this is, that I have several data.txt files and don't want to build a plot.gnu file for each of these.

I read about the special '-' file in this stackoverflow thread and I read about multiple plots in one file. However this would require to include the data with the gnuplot code, which isn't clean.

One can bet, you solve some optimization problem with population based algorithm ;) — John_West, Feb 19 '16 at 22:29

score 32 · Answer 1 · answered Jul 10 '13 at 16:58

If you are on a Unix system (i.e. not Windows) you can use '<cat' instead of '-' to read from stdin:

plot '<cat' using ...

Then you can do cat data.txt | gnuplot script.gp. However, in the specific case you mention in your question, with the plot in the for loop, you read the input three times. So sending the data through stdin is not appropriate, since the data will be gone after the first time it is read.

score 28 · Answer 2 · answered Jun 26 '15 at 18:57

28

not a direct answer but this is what i use to quickly look at data. it's especially helpful with the cut command

cat data.txt | cut -f2 -d' ' | gnuplot -p -e "plot '<cat'"

answered Jun 26 '15 at 18:57

kirill_igum

3,953
5
47
73

Note though that you won't be able to manipulate the plot in any way: e.g. drag, resize — even simply maximizing the window will make gnuplot quit, because the data are no longer available. – Ruslan Oct 13 '19 at 08:49
Didn't crash for me. gnuplot --version --> gnuplot 5.2 patchlevel 8 – randompast Apr 26 '23 at 20:30

score 19 · Answer 3 · answered Oct 13 '15 at 17:26

If you want to plot data coming from a pipe more than once, you need to store it somehow in memory. My preferred way is to use a temporary file in /dev/shm, which exists in most Linux systems and maps to RAM. Just to keep things clean, I set a trap to delete the temporary file at exit.

Example (using your data.txt):

cat data.txt | (cat > /dev/shm/mytempfile && trap 'rm /dev/shm/mytempfile' EXIT && gnuplot -e "set terminal dumb; plot for[col=2:4] '/dev/shm/mytempfile' using 1:col title columnheader(col) with lines")

Result:

12 ++------------+-------------+-------------+-------------+------------**
   +             +             +             +             + Best ****** +
   |                                                        Worst***#### |
10 ++                                              *******Average $$$$$$++
   |                                           ****                      |
   |                                        ***    $$$$               $$$$
 8 ++                                     **     $$    $$        $$$$$  ++
   |                                    **     $$        $$    $$        |
   |                               *****    $$$              $$       ####
 6 ++                          ****       $$ ############# $$    #####  ++
   |                         **         $$ ##             #  ####        |
   |                       **        $$$ ##                ##            |
   |                     **      $$$$  ##                                |
 4 ++         ***********   $$$$$  ####                                 ++
   |     *****  ###################                                      |
   | ****   $$##                                                         |
 2 **    $$$##                                                          ++
   #########                                                             |
   + $$          +             +             +             +             +
 0 $$------------+-------------+-------------+-------------+------------++
   0             2             4             6             8             10

Even nicer is to replace `set terminal dumb` with `set terminal dumb size $COLUMNS $LINES`, which takes current terminal size into account and stretches the output. — Ruslan, Oct 13 '19 at 09:00

score 15 · Answer 4 · answered Jul 09 '13 at 12:12

What's wrong with using the -e option of gnuplot from shell? You can provide a variable as input, say data.txt, from shell using:

gnuplot -e "filename='data.txt';ofilename='test.png'" plot.gnu

You should be able to call the above command multiple times with different values for "filename" from shell using a for loop.

And then you change your script plot.gnu to:

set terminal png
set output ofilename
plot for[col=2:4] filename using 1:col title columnheader(col) with lines

score 3 · Answer 5 · answered Jan 07 '14 at 14:20

How about using the system() command

set terminal png
set output "test.png"

# read shell input
# the echo prints the variable, which is then piped to gnuplot
fname = system("read filename; echo $filename")

plot for[col=2:4] fname using 1:col title columnheader(col) with lines

You can call it now with

echo "data.txt" | gnuplot script.gp

score -2 · Answer 6 · answered Nov 22 '13 at 10:06

-2

Mix both answers :

cat data.txt | gnuplot -e "set terminal png; set output "test.png"; plot for[col=2:4] '<cat' using 1:col title columnheader(col) with lines

answered Nov 22 '13 at 10:06

user1264274

1

1

This doesn't work, since reading from stdin can't be combined with a for loop in gnuplot. See http://stackoverflow.com/questions/4981279/how-to-make-several-plots-from-the-same-standard-input-data-in-gnuplot for workarounds. – ramn Dec 10 '13 at 15:41

pipe plot data to gnuplot script

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