Hello list, Hi Eric, I stumbled upon the old thread "ploting matrix data" and the changes in my mpl-svn working copy allowing to provide under_color and over_color as a keyword argument of contourf.
On Tuesday 14 April 2009 20:39:06 Eric Firing wrote:
> Matthias Michler wrote:
[snip]
> > Second question: Could it be useful to add two kwargs 'over_color'
> > and 'under_color' to contourf in order to allow specification of a
> > extended ListedColormap by kwarg 'colors' and these two colors?
> > I tried to include this in the attached patch
> > (added_under_and_over_color_to_ContourSet.patch) and use it in the
> > example contourf_with_extended_colorbar_new.py. But it dosn't work
> > completely correct. Although the over color is correctly set to cyan in
> > the cmap In [14]: my_contourf.cmap._rgba_over
> > Out[14]: (0.0, 1.0, 1.0, 1.0)
> > red is used for values above the colormap-bounds.
> >
> > Thanks in advance for any comments and hints.
>
> I need to look at your patch--but a priori, I am a bit worried about the
> tendency of APIs to get more and more complicated, with more and more
> kwargs, as time goes on.
>
> Eric
First of all I think my previously described error in the over-color is due to
a bug in the set up of the colors.ListedColormap during the initialisation of
ContourSet if 'self.colors' is not None.
For the number of entries in the map 'N' the number of layers is
passed "N=len(self.layers)", which is not useful if self.extend is 'both'.
Let's say I want 3 regions and provide 3 colors. If extend is 'both' the
number of layers is the #{colored regions between min and max} + 2 = 5. For
N=5 in the initialisation of the ListedColormap the list of colors is
extended to have length 'N=5' (by repetition). Therefore an additional layer
(more precisely 2) occurs in the colormap and although the over_color is set
to something different the (repeted) first element of 'colors' is used to
color values above the highest level.
I propose the following case differentiation:
if self.extend == "both":
N = len(self.layers) - 2
elif self.extend in ('max', 'min'):
N = len(self.layers) - 1
else:
N = len(self.layers)
Maybe N = len(self.levels) - 1 is always a good solution.
Is this a bug and does my proposal resolve it without destroying something
else?
Now back to my previous proposal to include the additional keyword
arguments 'under_color' and 'over_color'.
I attached two scripts, which show the difference between the old and the new
usage of a listed colormap specifing under/over_color. In the old behavior
you have to set the under and over color after setting up the contour.
my_contourf.cmap.set_over('cyan')
my_contourf.cmap.set_under('yellow')
and in the new behavior you can pass
over_color='cyan', under_color='yellow',
to the contourf-function.
Could these keyword arguments be useful?
Thanks in advance for any comments.
Kind regards,
Matthias
contourf_with_extended_colorbar_NEW.py
Description: application/python
contourf_with_extended_colorbar_OLD.py
Description: application/python
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