Question

So I’m looking for some quick-and-dirty solution.

The problem:

I am trying to plot a specific section of a data file with gnuplot. This is fine. The basic line goes something like

plot "<(sed -n '1,100p' pointsandstuff.dat)" u 1:log($4**2+$5**2) notitle

This works just fine. The next step I want is to include in my title another part of the data, namely the data entry $3 (which for the points listed is identical, so I can parse it from anywhere). I run into problem because, while plot seems fine, I can’t seem to feed regex info into ‘title’. An example of something that doesn’t work”

plot "<(sed -n '1,100p' pointsandstuff.dat)" u 1:log($4**2+$5**2) title "<(sed -n '1,1p' pointsandstuff.dat)"

(This would spit out a whole data line, in theory, though in practice I just get the title “<(sed…”)

I tried attacking this with a bash script, but the ‘$’s that I use throw the bash script into a tizzy:

#!/bin/bash


STRING=$(echo|sed -n '25001,25001p' pointsandstuff.dat)
echo $STRING


 gnuplot -persist << EOF
 set xrange[:] noreverse nowriteback
 set yrange[:] noreverse nowriteback

 eval "plot "<(sed -n '25001,30000p' pointsandstuff.dat)" u 1:log($4**2+$5**2) title $STRING


EOF

Bash won’t know what to do with ‘$4’ and ‘$5’.

Answer 1

Aha, thanks all. Have come up with a few solutions by now–the simplest being just escaping those $s from before (which I mistakenly thought gnuplot disliked…). To whit:

STRING=$(echo|sed -n '1,1p' spointsandstuff.dat)
echo $STRING


 gnuplot -persist << EOF
 set xrange[:] noreverse nowriteback
 set yrange[:] noreverse nowriteback

 eval "plot "<(sed -n '1,100p' pointsandstuff.dat)" u 1:(log(\$4**2+\$5**2)) title '$STRING'
 !gv diag_spec.eps &

EOF

Thanks all, though–it’s been a good excuse to play with this stuff…here’s hoping that, if any poor soul sees this script later, it might be a bit easier on them.