I have a problem that arose when I tried to run the gridding irregularly
spaced data demo on the wiki
http://www.scipy.org/Cookbook/Matplotlib/Gridding_irregularly_spaced_data
When I run the attached script, which sets one value of an array to nan,
masks the array where there are nan, and tries to plot it using
contour(), I get the following errors:
/usr/lib/python2.4/site-packages/numpy/core/ma.py:604: UserWarning:
Cannot automatically convert masked array to numeric because data
is masked in one or more locations.
warnings.warn("Cannot automatically convert masked array to "\
Traceback (most recent call last):
File "masked_nan.py", line 18, in ?
contour(x, y, z)
File "/usr/lib/python2.4/site-packages/matplotlib/pylab.py", line
1754, in contour
ret = gca().contour(*args, **kwargs)
File "/usr/lib/python2.4/site-packages/matplotlib/axes.py", line
4092, in contour
return ContourSet(self, *args, **kwargs)
File "/usr/lib/python2.4/site-packages/matplotlib/contour.py", line
429, in __init__
x, y, z = self._contour_args(*args) # also sets self.levels,
File "/usr/lib/python2.4/site-packages/matplotlib/contour.py", line
614, in _contour_args
lev = self._autolev(z, 7)
File "/usr/lib/python2.4/site-packages/matplotlib/contour.py", line
517, in _autolev
zmargin = (zmax - zmin) * 0.001 # so z < (zmax + zmargin)
TypeError: unsupported operand type(s) for -: 'str' and 'str'
I am using
>>> numpy.__version__
'1.0'
>>> matplotlib.__version__
'0.87.7'
Is there a way to use contour() and plot arrays whose elements may be nan?
Thanks,
Paul
import matplotlib
import numpy
import numpy.core.ma as ma
from pylab import *
a = linspace(0, 1, 3)
b = linspace(0, 1, 3)
x, y = meshgrid(a, b)
z = x + y
z[0][0] = numpy.nan
z = ma.masked_where(numpy.isnan(z), z)
contour(x, y, z)
show()
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