Re: Non-linear axis data in imagesc

[Daniel Arteaga]

On 02/12/11 14:29, Ben Abbott wrote:
> On Dec 2, 2011, at 8:20 AM, Daniel Arteaga wrote:
>
> > On 02/12/11 14:15, Ben Abbott wrote:
> > > On Dec 2, 2011, at 6:52 AM, Daniel Arteaga wrote:
> > >
> > > > Hi all,
> > > >
> > > > imagesc fails to display correctly non-linarly spaced axes. Instead it 
> > > > "invents" linear axis from the maximum value. See what I mean:
> > > >
> > > > x = logspace(0,5,20);
> > > > y = logspace(0,2,10);
> > > > A = rand(10,20);
> > > > imagesc(x,y,A);
> > > >
> > > > Is this a bug? Any workaround to get the correct behaviour?
> > > >
> > > > Tested using GNU Octave Version 3.4.2 under Ubuntu 11.10.
> > > >
> > > > Thank you,
> > > >
> > > > Daniel
> > >
> > > If you see (0,0) in the upper-left, then it is working as intended. Matlab 
> > > behaves this way as well.
> >
> > Sorry, I was not meaning that. What I was meaning is that the axis labels do 
> > not correspond to the x vector defined above. The real axis should be 
> > logarithmic, but imagesc invents a linear axis.
> >
> > Thank you,
> >
> > Daniel
>
> Ok. That *feature* is also inherited from Matlab.
>
> I've attached the result from Matlab (R2011b). Does it look the same as what 
> Octave produces for you?

Yes, the result is essentially the same.

Anyway, be in Matlab or Octave, the result is incorrect as I understand, 
since it is assigning values to the axis that do not match with the 
plotted data.

In other words, for a given x and y value (according to the displayed 
axis), the color plotted is not the correct one.

In my opinion, at least a warning should be displayed in this situation.

Thank you very much,

Daniel