Re: using gnuplot as a filter

[Ethan M. <merritt@u.washington.edu>]

On Tuesday 11 December 2007 02:32, P=C3=A1draig Brady wrote:
> I tried to get a gnuplot script to read
> from stdin like a normal linux filter using plot '-'

It certainly works in general.  Consider the following trivial example,
which draws a big red triangle:
    plot '-' with filledcurve
      1 1
      2 3
      3 2
      e

Could you please provide a specific example in which it doesn't work?


> I know how to work around this but it's a horrible hack.
> I.E. rather than:
>   gen_data | ./plot.gp > file.png

Erk.  What is that supposed to be doing?


I suspect that the gnuplot command
       plot '-'
doesn't mean what you think it does.
It does not mean "read from original stdin of parent process";
it means "read from the current input stream".
Assuming that the file ./plot.gp calls gnuplot, that means that
plot '-' will read from the file plot.gp.

Please explain exactly what you are trying to do, so that we can
suggest alternatives.

> one needs to do:
>   (cat plot.gp; gen_data) | gnuplot > file.png

That command makes no sense to me.  Maybe you want this?

file plot.gp contains:
   set term png
   system "gen_data > temp.dat"
   plot "temp.dat"

gnuplot plot.gp > file.png




=2D-=20
Ethan A Merritt            Courier Deliveries: 1959 NE Pacific
Dept of Biochemistry
Health Sciences Building
University of Washington - Seattle WA 98195-7742