tics of log color axis

[John W. Eaton]

On 27-May-2009, Petr Mikulik wrote:

| > | I have noticed two problems related to log color axis. These bugs are in 
| > | Octave 3.1.55 (while in Octave 3.0.x it does not work "at all"):
| > | 
| > | A. Wrong tic labels in figure 2:
| > |   figure(1)
| > |   imagesc(1./hilb(99)); h=colorbar;
| > |   figure(2)
| > |   imagesc(1./hilb(99)); h=colorbar; set(h,'yscale','log');
| > 
| > I'm not sure why this is happening.  I've extracted the commands from
| > the gnuplot stream that generate the colorbar and attached them
| > below.  If you can tell me what we should be sending to gnuplot to get
| > the correct behavior, I might be able to fix Octave to generate the
| > correct set of commands.
| 
| I think that the 2nd set of "plot - with image" draws the colorbar. I guess 
| these (binary) numbers should be log10.

I don't think that's it.  Try adding

  set logscale y

to the debug.gp file I sent.  Do you get something like what I've
attached below?  You can see this same effect with

  imagesc (1./hilb(99));
  set (gca, 'yscale', 'log');

in Octave.  I have no clue why the image is squeezed just by setting
logscale on the axis.

Why should we need to set logscale on the Y axis if we are only using
the Y2 axis?  Is that a limitation of gnuplot?  For example, when I
execute the following commands in gnuplot, the y2 tick marks appear to
be linearly spaced and the y2 tick labels do not appear:

  set logscale y2
  plot sin (x) axes x1y1, exp (x) axes x1y2

but after executing
 
  set logscale y
  replot

they do appear, but then the y1 axis is also log scaled.  Is is
possible to set them independently?

I'm using gnuplot 4.2.5.

jwe

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