From bug-octave-request at bevo dot che dot wisc dot edu  Sat Sep 26 00:26:13 1998
Subject: octave bug (plot command)
From: "John W. Eaton" <jwe at bevo dot che dot wisc dot edu>
To: Juergen dot Weith at t-online dot de (juergen.weith@t-online.de)
Cc: bug-octave at bevo dot che dot wisc dot edu
Date: Sat, 26 Sep 1998 00:26:11 -0500 (CDT)

On 30-Jul-1998, juergen dot weith at t-online dot de <Juergen.Weith@t-online.de> wrote:

| yesterday I found a strange behaviour of octave. Please find below my bug 
| report. Btw, thanks for maintaining this great tool, I am doing all my 
| computations with octave and it works very well ...
| 
|                                                       Best regards
| 
|                                                         Juergen
| -----------------BUG REPORT-----------------------------------------------------
| 
| Octave vers. used: 2.0.13 (i486-pc-linux-gnulibc1)
| Linux kernel:      2.0.33
| Configuration:     ./configure --enable-shared --enable-dl --enable-lite-kernel
| 
| Description:       A problem occurs when using the plot command to draw more    
|                    than one curve in one corordinate system and generating fig 
|                    output.
| 
| Example:          Consider the following simple program:
|                     gset term fig;               % set to fig output
|                     gset output "dummy.fig";	 % direct to file dummy.fig
|                     x=(0:99)'/100*2*pi;          % example data sequence
|                     s1=sin(x);                   % generate sine samples
|                     s2=2*cos(x);                 % generate cosine samples
|                     sigs=[x s1 s2];              % Construct a matrix to plot
|                     plot(sigs(:,1),sigs(:,2),sigs(:,3),sigs(:,4));
|                     closeplot;
| 
|                   The plot output in dummy.fig looks strange. It seems to me    
|                   that calling plot executes two single plot commands each      
|                   of which is scaled separately (whereas scaling should be done 
|                   once only). 
| 
|                   Hoewver replacing the plot command by 
|                     gplot sigs using 1:2, sigs using 1:3 
|                   results in a c o r r e c t  output.

Yes, because the plot command eventually generates something like the
following sequence of gnuplot commands

  plot sigs using 1:2
  replot sigs using 1:3

(This is the same problem that someone else reported earlier about the
postscript terminal type and that I just responded to a few minutes
ago).

The workaround is to set up the plot to the screen (or /dev/null) and
then use replot to generate the final file.  As I said earlier, the
plot command could probably be fixed to avoid the problem, but doing
that's not high on my list.  Any volunteers?

jwe