Hi Eric, thanks for the tip about the legend.
Regarding the data, assuming i am using pcolor, am I right in thinking
that using Boundarynorm would be the best way to control the colors for
each code?
Mat,
I think BoundaryNorm is overkill and/or awkward for your case. It sounds like you don't have ordinary values, but rather a set of labels that happen to be integers. I would use a ListedColormap and then use sequential integers as the C values to index directly into the colormap:
C = np.array([[0,1,2],[2,0,1]])
import matplotlib.colors as mcolors
cmap = mcolors.ListedColormap(['r', 'g', 'lightgray'])
pcolor(C, cmap=cmap, norm=mcolors.NoNorm())
Of course you would need to map your sequence of numbers (-8888, 0, ...) to a sequence of integers starting at zero.
The key point is that the NoNorm() instance leaves your original C values alone, and since they are integers, they are then used directly as indices.
You could also make your own mcolors.Normalize subclass which would process your labels and return either a float in the 0-1 range, or an integer for direct indexing.
When you need only a very few colors, the ListedColormap with direct indexing is nice because it allows you to specify those colors using any valid color specification method.
Eric
···
On 04/09/2012 08:17 AM, Mathew Topper wrote:
Thanks
Mat
On 04/09/2012 06:26 PM, Eric Firing wrote:
On 04/09/2012 02:22 AM, Mathew Topper wrote:
Dear matplotlib-users,
I have a spatial data set that has coded values for each cell, which are
limited to just a few numbers, ie -8888, 0, 100, and 9999. I would like
to display this data with a plot similar to pcolor, but I don't want a
colorbar, I want a legend showing the colors for each code and an
explanation for what each code represents. I would like to be able to
choose a subset of the codes as well, for example just plotting the 0
and 100 codes and ignoring the -8888 and 9999 codes.
I have seen a few similar attempts that used BoundaryNorm, but I don't
want to show a range of values I just want to set colors for a few
explicit values. Those examples also had a colorbar and, as I said, I
would prefer a legend.
Can anyone offer any tips?
For the plot itself you can use pcolor if your data are on a
quadrilateral grid, or a PathCollection or PolyCollection otherwise.
For the legend, you can use proxy artists:
http://matplotlib.sourceforge.net/users/legend_guide.html#using-proxy-artist
Eric
Thanks
Mat
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