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From: Ethan Merritt <eamerritt@gmail.com>
Newsgroups: comp.graphics.apps.gnuplot
Subject: Re: Histograms, re-use auto yrange
Date: Wed, 23 Jan 2019 04:59:26 -0000 (UTC)
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On Tue, 22 Jan 2019 08:36:23 -0800, Stephen Prather wrote:

> Hi forum--
> 
> I am trying to plot multiple histograms, but I want them all to have the same yrange so that the bars are visually comparable across plots. BUT, I also want gnuplot to auto-range the y axis. I don't mind plotting in two passes (plot all, capture max yrange, replot all). But I don't know how to query the value of the yrange into a variable. I know about 'show yrange'. But I don't know how to use that information. I could script around gnuplot (ie, Ruby), but if I'm going to do that, I just as well write my own bucketizer in Ruby to determine the max height of buckets across my datasets.

set yrange [*:*] writeback
plot 'first-histogram' ...
set yrange restore
plot 'other-histograms'

Here is the relevant help text from the documentation:

 The `writeback` option essentially saves the range found by `autoscale` in
 the buffers that would be filled by `set xrange`.  This is useful if you wish
 to plot several functions together but have the range determined by only
 some of them.  The `writeback` operation is performed during the `plot`
 execution, so it must be specified before that command.  To restore,
 the last saved horizontal range use `set xrange restore`.  For example,
       set xrange [-10:10]
       set yrange [] writeback
       plot sin(x)
       set yrange restore
       replot x/2
 results in a yrange of [-1:1] as found only from the range of sin(x); the
 [-5:5] range of x/2 is ignored.  Executing `show yrange` after each command
 in the above example should help you understand what is going on.




> Since gnuplot is not a general programming language, I think this may be too tall of an order. Sure would be cool if it were a full language (or re-built on top of an existing one).
> 
> Thanks!
> --Myles