By the way, I had some success with this, but my approach is really
inefficient. Perhaps someone could suggest how I can improve the following:
import matplotlib.numerix as nx
from numarray import ma
def enumimage(A,colors):
"""
Create an image from a matrix of enumerated values
A is a matrix
colors is a dictionary mapping enumerated values to (r,g,b,a) tuples
If a value in A is masked, the resulting image will be transparent
If a value in A is not present in the color map, it will plot black.
"""
B = nx.zeros((nx.size(A,0),nx.size(A,1),4))
mask = A.mask()
for r in range(nx.size(A,0)):
for c in range(nx.size(A,1)):
v = A[r,c]
if mask[r,c]:
B[r,c,:]=[1,1,1,0]
else:
try:
B[r,c,:]=colors[v]
except KeyError,e:
B[r,c,:]=[0,0,0,1]
return B
if __name__=='__main__':
import pylab
A = nx.array([[1,2,7],[1,2,2],[1,1,9]])
print "A =",A
A1 = ma.array(A,mask=ma.where(A==1,1,0))
print "A1 =",A1
colors={
2:(1,0,0,1)
,7:(0,1,0,1)
}
B = enumimage(A1,colors)
print "B =",B
pylab.figure()
pylab.hold()
pylab.imshow(B,interpolation='nearest',extent=0.5+nx.array([0,nx.size(A,0),nx.size(A,1),0]))
pylab.axes
pylab.show()
John Pye wrote:
> Hi all
>
> I have some data with enumerated values in an array. Values are like
> 1,2,7,9 spread around in the array. I want to plot those values so that
> I can see the 'regions' in my data, then I want to overlay this with
> some contour lines drawn from other data.
>
> I want to be able to specify the colors for each of the enumerated
> values, as they need to be consistent throughout my work. My array of
> enumerated values is *masked* so that there are areas where I don't want
> to show anything (this would plot as transparent pixels).
>
> Has anyone got suggestions on the best way of doing this? It seems that
> the technique in
> http://www.scipy.org/Cookbook/Matplotlib/Plotting_Images_with_Special_Values
> might be overkill, right? It also seemed that it had some problems with
> masked arrays.
>
> Cheers
>
> JP
>
>
--
John Pye
School of Mechanical and Manufacturing Engineering
The University of New South Wales
Sydney NSW 2052 Australia
t +61 2 9385 5127
f +61 2 9663 1222
mailto:john.pye_AT_student_DOT_unsw.edu.au
http://pye.dyndns.org/
_______________________________________________
Matplotlib-users mailing list
Matplotlib-users@lists.sourceforge.net
https://lists.sourceforge.net/lists/listinfo/matplotlib-users
