[Octave-bug-tracker] [bug #54610] imagesc doesn't implement ranges properly

[Brent Baccala]

URL:
  <http://savannah.gnu.org/bugs/?54610>

                 Summary: imagesc doesn't implement ranges properly
                 Project: GNU Octave
            Submitted by: baccala
            Submitted on: Fri 31 Aug 2018 09:50:09 PM UTC
                Category: Plotting with OpenGL
                Severity: 3 - Normal
                Priority: 5 - Normal
              Item Group: Incorrect Result
                  Status: None
             Assigned to: None
         Originator Name: 
        Originator Email: 
             Open/Closed: Open
         Discussion Lock: Any
                 Release: 4.4.1
        Operating System: GNU/Linux

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Details:

The `imagesc` documentation states:

The axis values corresponding to the matrix elements are specified in x and y,
either as pairs giving the minimum and maximum values for the respective axes,
or as values for each row and column of the matrix img.

`imagesc` doesn't seem to be properly respecting the limits when they're given
as pairs.  For example,


figure()
xlim([-1,1])
ylim([-1,1])
imagesc([-1,1], [-0.5, 0.5], 1:10)


What I expect is a colored band in the middle of the figure, since I specified
the y range as a pair giving -0.5 and 0.5 as the minimum and maximum values,
respectively, yet the figure's y limits go from -1 to 1.

What I get is a colored band that fills the entire figure.  I've tested this
with Octave 4.4.1 on Ubuntu 18.04.

I've looked at the code, and I think the problem is at lines 3665-3667 in
gl-render.cc (4.4.1 release).

My first question, though, is am I understanding the documentation and the
intent correctly?  Do we agree that this is a bug?






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