Question

I found many solutions to this question for GNUPlot 4.2+ using title column, columheader etc. However, I am stuck with GNUPlot 4.0 and need to find a way to automatically set the titles using the top row of my data set.

I’m using a bash script to generate a dynamic (-> changes daily) file with data and I have a static .gnu file that contains the gnuplot settings.

Do you have any suggestions?

(Perhaps a way to use a variable/array inside the .gnu file?)

Answer 1

The trick is using the Command Substitution

Sample Code:

# content of file
$ cat data.txt
header
1
2
3
4
5

# generate gnuplot script
$ echo "set term dumb; plot '<(tail -n +2 data.txt)' title '$(head -1 data.txt)'"
set term dumb; plot '<(tail -n +2 data.txt)' title 'header'

# pipe to gnuplot 
$ echo "set term dumb; plot '<(tail -n +2 data.txt)' title '$(head -1 data.txt)'" | gnuplot

# or you can use `here-doc` (note: `>` is bash prompt)
$ gnuplot <<_EOF_
>    set term dumb
>    plot '<(tail -n +2 data.txt)' title '$(head -1 data.txt)'
>_EOF_

    5 ++-------+--------+-------+--------+--------+--------+-------+-------+A
      +        +        +       +        +        +        +  header   A    +
  4.5 ++                                                                   ++
      |                                                                     |
      |                                                                     |
    4 ++                                                   A               ++
      |                                                                     |
  3.5 ++                                                                   ++
      |                                                                     |
      |                                                                     |
    3 ++                                 A                                 ++
      |                                                                     |
  2.5 ++                                                                   ++
      |                                                                     |
      |                                                                     |
    2 ++                A                                                  ++
      |                                                                     |
  1.5 ++                                                                   ++
      |                                                                     |
      +        +        +       +        +        +        +       +        +
    1 A+-------+--------+-------+--------+--------+--------+-------+-------++
      0       0.5       1      1.5       2       2.5       3      3.5       4

Note: $(head -1 data.txt) expand to header before passing to Gnuplot.