matplotlib-users

[Matplotlib-users] origin='upper' nor working with pcolor

[Khem R. <raj...@gm...>]

Hi

I have been trying to plot a matrix and want to start from top left
corner. I tried to use 'matshow' and it worked the way I wanted but
that could not satisfy other needs like I needed to plot something
else over the matrix and also needed shading='faceted' which I could
not set using matshow

So I tried to use 'pcolor' where shading is faceted by default and I
could plot other stuff on top ofI the matrix image but I could not get
the origin='upper' working with pcolor. I also tried with imshow but
it did the same thing.

I tried both lower and upper values and results come out same the
array starts plotting from bottom left.

I am using 0.87.6 and python 2.4.3

Has anybody seen this problem ? Is there usage error?

Re: [Matplotlib-users] origin='upper' nor working with pcolor

[Eric F. <ef...@ha...>]

Khem Raj wrote:
> Hi
> 
> I have been trying to plot a matrix and want to start from top left
> corner. I tried to use 'matshow' and it worked the way I wanted but
> that could not satisfy other needs like I needed to plot something
> else over the matrix and also needed shading='faceted' which I could
> not set using matshow

matshow calls imshow.

You should be able to plot on top of an image made by matshow or imshow, 
so I don't know what the problem was with that.

> 
> So I tried to use 'pcolor' where shading is faceted by default and I
> could plot other stuff on top ofI the matrix image but I could not get
> the origin='upper' working with pcolor. I also tried with imshow but
> it did the same thing.

pcolor does not have an 'origin' kwarg but imshow does, so I don't 
understand your last sentence above.

For pcolor you need to either rearrange your matrix (e.g., 
'pcolor(flipud(Z))') or call pcolor with X and Y arguments as well as Z.

Eric