Re: [Matplotlib-users] pcolor with non-integer axes?

[Park H. <par...@gm...>]

Eric,

Python 2.5 (precompiled binary)
SciPy 0.5.2 (precompiled binary)
matplotlib 0.8737 (win32-py2.5 precompiled binary)
and if it matters I'm running in iPython for all this work.

The script is:
----
from scipy import *
from pylab import *
import matplotlib.numerix.ma as ma

N = 10
y = linspace(0, pi, N)
x = linspace(0, pi, N)
z = randn( N, N)
zm = ma.masked_where( z > 0.3, z)

pcolor( x, y, zm)

----

and the result I get is:

----
In [11]: execfile('pcolor_issue.py')
---------------------------------------------------------------------------
<type 'exceptions.ValueError'>            Traceback (most recent call last)

C:\Documents and Settings\phays\My Documents\NDS\PDOP\<ipython console> in
<module>()

C:\Documents and Settings\phays\My Documents\NDS\PDOP\pcolor_issue.py in
<module>()
      7 x = linspace(0, pi, N)
      8 z = randn( N, N)
      9 zm = ma.masked_where( z > 0.3, z)
     10
---> 11 pcolor( x, y, z)

C:\apps\py\lib\site-packages\matplotlib\pylab.py in pcolor(*args, **kwargs)
   1941         hold(h)
   1942     try:
-> 1943         ret =  gca().pcolor(*args, **kwargs)
   1944         draw_if_interactive()
   1945     except:

C:\apps\py\lib\site-packages\matplotlib\axes.py in pcolor(self, *args,
**kwargs)

   3788             raise TypeError, 'Illegal arguments to pcolor; see
help(pcolor)'
   3789
-> 3790         Nx, Ny = X.shape
   3791
   3792         # convert to MA, if necessary.

<type ' exceptions.ValueError'>: need more than 1 value to unpack
----


On 3/29/07, Eric Firing <ef...@ha...> wrote:
>
> Pcolor accepts non-integer values of X and Y, so I don't know what the
> problem is.  Please post a minimal but complete script that illustrates
> the error, and say what version of mpl you are using. With moderately
> recent versions, using masked arrays should work fine.
>
> Eric
>
> Park Hays wrote:
> > I have bogus values I don't want to display in a gridded data set
> > (regions of non-convergence, for example).  pcolor does exactly what I
> > want with a masked array, except the X and Y arguments must be integer
> > arrays (as far as I can tell) and my data X and Y points are not integer
> > arrays.  An approximation of what is happening goes like:
> >
> > x = linspace( 0, pi, 100)
> > y = linspace( -pi/2, pi/2, 30)
> > ev = custom_func( x, y)
> > print sum( isnan( ev))
> >  12 (or whatever)
> >
> > ev_m = ma.mask_where( isnan( ev), ev)
> > pcolor( x, y, ev_m) <-- this will fail, with an error like "need more
> > than one value to unpack" which I think is caused by the non-integer
> > nature of x, y.
> >
> >
> > Any suggestions for how can I can address this?  My preference is to use
> > pcolor, because of the  transparency.  I am not a fan of the scipy
> > discussion regarding user-driven normalization "sentinels" to catch the
> > bogus values.  Masked arrays seem so much more flexible.
> >
> > -Park
>
>