From owner-help-octave at bevo dot che dot wisc dot edu  Fri Nov 29 09:49:43 1996
Subject: Re: Matlab ginput
From: Ted dot Harding at nessie dot mcc dot ac dot uk (Ted Harding)
To: chelle at bcgn dot grignon dot inra dot fr
Cc: help-octave at bevo dot che dot wisc dot edu
Date: Fri, 29 Nov 1996 15:04:09 +0000 (GMT)

( Re Message From: chelle at bcgn dot grignon dot inra dot fr )
> 
> I think that's impossible, because the use of gnuplot to draw graphics, but,
> I 'd like to know if it exists an octave function that allows to specify
> on the graphic window, several points or domain with the mouse and to
> retrieve this data in an octave object. I think there is a matlab
> function (~ginput()) that does this.

There is indeed such a MatLab function (and very useful it can be).
However, there is no such function with octave-1.1.1.

Nor, so long as graphics depends on gnuplot, is there likely to be: the
gnuplot display does its work independently of octave once it has received
the input from octave: only gnuplot knows where on the screen the
coordinates are plotted, and gnuplot won't tell. You can't use the mouse
to ask gnuplot for the coordinates of points it has plotted.

However, if a different graphics package were used (which one, anyone?),
which had the capability of outputting the coordinates of points selected
by the mouse, then it would be possible to write such an octave function.
Either the coordinates could be written to a file which could be read by
octave. or maybe pipes or sockets could be used.

The statistical software package xlispstat is very good at graphics, and
allows this sort of selection very flexibly. I have been toying with the
idea of interfacing octave to it (but would have to grapple with LISP).

Another possible benefit that could result from such a step would be the
possibility of dynamic graphing -- adding points/lines to a plot in real
time as they are computed.

Has anyone else any ideas along these lines, or has gone further into
xlispstat or similar than I have?

Best wishes to all,
Ted.                                    (Ted dot Harding at nessie dot mcc dot ac dot uk)