Re: [Gnuplot-info] how to make diff-plot?

[Hans-Bernhard B. <br...@ph...>]

On Thu, 9 Sep 2004, Ole Jacob Hagen wrote:

> I have datafile, with 3 columns, where column 1 indicates samplenumber, 
> while col. 2 and col. 3 is values.
> I want to make a diff-plot, but how can I accomplish this?

By using tools outside gnuplot.  gnuplot isn't really a number crunching
utility, and trying to use it as one is bound to fail sooner or later.

A little awk script does this quite nicely.  Here's one from my
collection:

#! /bin/awk -f
BEGIN { firstline = 1 }

$0 !~ /^#/ { if (firstline == 1) {
    old_x = $1
    old_y = $2
    firstline = 0
  } else {
    print (old_x + $1)/2.0, "\t", (old_y - $2)/(old_x - $1), "\t"
    old_x = $1
    old_y = $2
  }
}


-- 
Hans-Bernhard Broeker (br...@ph...)
Even if all the snow were burnt, ashes would remain.