using gnuplot's corners2color c3 causes bad colored surfaces

[John W. Eaton]

On 24-May-2009, Dr. Johannes Zellner wrote:

| To: bug at octave.org
| Cc: johannes at zellenr.org
| Subject: using gnuplot's corners2color c3 causes bad colored surfaces
| 
| Bug report for Octave 3.0.5 configured for x86_64-pc-linux-gnu
| 
| Description:
| -----------
| 
| Plotting symmetrical data e.g.
| 
|    0   0   0   0   0
|    0   1   1   1   0
|    0   1   1   1   0
|    0   1   1   1   0
|    0   0   0   0   0
| 
| with surf or surface causes unsymmetric coloring.
| 
| 
| Fix:
| ---
| 
| replace occurences of "corners2color c3" in __go_draw_axes__.m by
| "corners2color mean".

Doing that seems to make a plot with colors that are not like what
Matlab produces, so if we make this change, I suspect someone else
will report the difference as a bug.

jwe