Re: [Matplotlib-users] alternative to imshow with polar axes ?

[Benjamin R. <ben...@ou...>]

On Thu, Mar 10, 2011 at 8:40 AM, Auré Gourrier
<aur...@ya...>wrote:

> Dear all,
>
> Once again, I turn for help.
> I'm trying to plot a polar image using colormap values for the theta values
> and increasing alpha values along the radius.
> I do this using imshow passing the rgba tuple at each pixel position which
> works very nicely with rectangular axes, but fails to display using polar
> axes (see code below).
> As usual, I've done a fair bit of digging to find where the problem is and
> whether I could make out an alternate solution but haven't managed to come
> through. I've tried using pcolormesh but I don't see how to pass the rgba
> tuple
> Can anyone point me in the right direction.
> I'm using matplotlib 1.0.1 and Python 2.4
>
> Cheers,
>
> Auré
>
>
It appears that imshow() (and matshow()) do not support non-rectilinear
axes.  I don't know if this is a bug or if there is no way to make it
support polar projections.  Hopefully, someone else more knowledgable could
chime in on this.

I am also not exactly sure how to accomplish what you want using pcolor.  A
really slow, painful way would be to pcolor each row with the rest masked
out, setting the alpha value for that row.  I have long wondered if the
alpha kwarg in various functions could be improved by allowing array values
and take advantage of numpy broadcasting.

Ben Root