CODEWITHSUNDEEP
shellgnuplot
sn8ze
sn8ze

Reputation: 27

gnuplot replot not plotting

The short version:

gnuplot's "replot" command is not seeming to plot anything. Only the original plot ("plot ...") is displayed in the output.

The long version:

I have a shell script cycling through a database of files, some of which need to be plotted in the same output image, some don't. My approach currently is to have the shell script write a gnuplot script ... something along these lines:

directory of input files, "data"

1_1.csv
1_2.csv
1_3.csv
1_4.csv
2_1.csv
...
x_y.csv

shell.sh

for f in data/*.csv
do
    gpFile=scripts/gp_x.gp      # x from input filename
    out=out_x.png               # x from input filename
    if [ ! -e "$gpFile" ]; then       # if gnuplot script does not exist
        cat <<-EOF >$gpFile           # create new file called gp_x.gp
        set datafile separator ","
        set term png size 1024,768
        set autoscale fix
        set output $out
        plot "$f" using 1:2 with lines
        EOF
    else                              # file does exist
        cat <<-EOF >>$gpFile          # append file with more text
        replot "$f" using 1:2 with lines
        EOF
    fi
done

for s in scripts/*.gp  # cycle through all scripts just generated
    gnuplot $s         # run gnuplot scripts
done

So that shell script generates a number of gnuplot scripts, one of which would look like this:

gp_x.gp

set datafile separator ","
set term png size 1024,768
set autoscale fix
set output out_x.png
plot "x_1.csv" using 1:2 with lines
replot "x_2.csv" using 1:2 with lines
replot "x_3.csv" using 1:2 with lines
replot "x_4.csv" using 1:2 with lines

This results in only plotting the first "plot" command, and none of the "replot" commands are accomplished (also, no errors are thrown). If I were to replace it with something like...

plot "x_1.csv" using 1:2 with lines, \
     "x_2.csv" using 1:2 with lines, \
     "x_3.csv" using 1:2 with lines, \
     "x_4.csv" using 1:2 with lines

It works fine. However, due to some complications in my actual program (this is extremely simplified), it's not really feasible to simply concatenate an extra line like that without the risk of breaking the script (e.g. having arguments with no command). And either way, I'd like to know why "replot" doesn't seem to work this way (or, more likely, what I'm doing wrong). Thanks!

Upvotes: 2

Views: 2094

Answers (1)

user8153
user8153

Reputation: 4095

plot "x_1.csv" using 1:2 with lines, \
     "x_2.csv" using 1:2 with lines, \
     "x_3.csv" using 1:2 with lines, \
     "x_4.csv" using 1:2 with lines

creates a single plot with four lines.

plot "x_1.csv" using 1:2 with lines
replot "x_2.csv" using 1:2 with lines
replot "x_3.csv" using 1:2 with lines
replot "x_4.csv" using 1:2 with lines

creates four plots: the first with one line, the second with two lines, and so forth. It is equivalent to

plot "x_1.csv" using 1:2 with lines
plot "x_1.csv" using 1:2 with lines, "x_2.csv" using 1:2 with lines
plot "x_1.csv" using 1:2 with lines, "x_2.csv" using 1:2 with lines,  "x_3.csv" using 1:2 with lines
plot "x_1.csv" using 1:2 with lines, "x_2.csv" using 1:2 with lines,  "x_3.csv" using 1:2 with lines, "x_4.csv" using 1:2 with lines

If you used a terminal that supports multiple pages (like pdfcairo) you would get four pages.png does not support that, and you see only the first plot.

Upvotes: 3

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