DOC: Update docs about qualitative colormaps

endolith · endolith · commit 80fa23e64600 · 2015-12-04T01:01:50.000-05:00
They are now ListedColormap; remove note about them being possibly
removed.

Add notes to What's New and API Changes.

Also added reminder to update the colormap documentation if you add a
new colormap or change an existing one
diff --git a/doc/api/api_changes/qualitative colormaps.rst b/doc/api/api_changes/qualitative colormaps.rst
@@ -0,0 +1,11 @@
+Qualitative colormaps
+---------------------
+
+Colorbrewer's qualitative/discrete colormaps ("Accent", "Dark2", "Paired",
+"Pastel1", "Pastel2", "Set1", "Set2", "Set3") are now implemented as
+``ListedColormap`` instead of ``LinearSegmentedColormap``.
+
+To use these for images where categories are specified as integers, for
+instance, use::
+
+    plt.imshow(x, cmap='Dark2', norm=colors.NoNorm())
diff --git a/doc/users/whats_new/qualitative colormaps.rst b/doc/users/whats_new/qualitative colormaps.rst
@@ -0,0 +1,9 @@
+Qualitative colormaps
+---------------------
+
+ColorBrewer's "qualitative" colormaps ("Accent", "Dark2", "Paired",
+"Pastel1", "Pastel2", "Set1", "Set2", "Set3") were intended for discrete
+categorical data, with no implication of value, and therefore have been
+converted to ``ListedColormap`` instead of ``LinearSegmentedColormap``, so
+the colors will no longer be interpolated and they can be used for
+choropleths, labeled image features, etc.
diff --git a/lib/matplotlib/_cm.py b/lib/matplotlib/_cm.py
@@ -2,7 +2,8 @@
 Nothing here but dictionaries for generating LinearSegmentedColormaps,
 and a dictionary of these dictionaries.
 
-Documentation for each is in pyplot.colormaps()
+Documentation for each is in pyplot.colormaps().  Please update this
+with the purpose and type of your colormap if you add data for one here.
 """
 
 from __future__ import (absolute_import, division, print_function,
diff --git a/lib/matplotlib/pyplot.py b/lib/matplotlib/pyplot.py
@@ -2060,11 +2060,9 @@ def colormaps():
 
     ColorBrewer Qualitative:
 
-    (For plotting nominal data, :class:`ListedColormap` should be used,
+    (For plotting nominal data, :class:`ListedColormap` is used,
     not :class:`LinearSegmentedColormap`.  Different sets of colors are
-    recommended for different numbers of categories.  These continuous
-    versions of the qualitative schemes may be removed or converted in the
-    future.)
+    recommended for different numbers of categories.)
 
     * Accent
     * Dark2
