Re: [Matplotlib-users] showing an image on log axes?

[Stefan v. d. W. <st...@su...>]

On Tue, Jun 13, 2006 at 06:21:22AM -0500, John Hunter wrote:
> setting the xscale and yscale to 'log' should work fine, as long as
> you make sure the xaxis and yaxis do not contain nonpositive limits.
> For an MxN image, the default limits are 0..N-1 and 0..M-1 and the 0
> will break the log transform.  You can work around this by setting the
> image "extent"
>=20
>   from pylab import figure, show, nx
>   fig =3D figure()
>   ax =3D fig.add_subplot(111)
>   im =3D nx.mlab.rand(500,500)
>   ax.imshow(im, extent=3D(1,501,1,501))

I often want to plot matrices, with the axes labeled according to the
matrix index.  I.e. the top-lefthand element should be (0,0) and the
bottom-righthand element (rows,columns).  Setting the extent does
work, i.e.

ax.imshow(im,extent=3D(1,columns,rows,1))

If others also use this frequently, it may be useful to have a quick
way of doing it (or maybe, there already is, and I've missed it).

Regards
St=E9fan