Merge pull request #27678 from rcomer/colors-from-colormap

rcomer · web-flow · commit 09eab5b1c471 · 2024-01-21T10:53:28.000Z
DOC: selecting individual colors from a colormap
diff --git a/.flake8 b/.flake8
@@ -63,6 +63,7 @@ per-file-ignores =
     galleries/users_explain/text/text_props.py: E501
 
     galleries/examples/animation/frame_grabbing_sgskip.py: E402
+    galleries/examples/color/individual_colors_from_cmap.py: E402
     galleries/examples/images_contours_and_fields/tricontour_demo.py: E201
     galleries/examples/images_contours_and_fields/tripcolor_demo.py: E201
     galleries/examples/images_contours_and_fields/triplot_demo.py: E201
diff --git a/galleries/examples/color/individual_colors_from_cmap.py b/galleries/examples/color/individual_colors_from_cmap.py
@@ -0,0 +1,61 @@
+"""
+===========================================
+Selecting individual colors from a colormap
+===========================================
+
+Sometimes we want to use more colors or a different set of colors than the default color
+cycle provides. Selecting individual colors from one of the provided colormaps can be a
+convenient way to do this.
+
+Once we have hold of a `.Colormap` instance, the individual colors can be accessed
+by passing it an index.  If we want a specific number of colors taken at regular
+intervals from a continuous colormap, we can create a new colormap using the
+`~.Colormap.resampled` method.
+
+For more details about manipulating colormaps, see :ref:`colormap-manipulation`.
+"""
+
+import matplotlib.pyplot as plt
+
+import matplotlib as mpl
+
+n_lines = 21
+
+cmap = mpl.colormaps.get_cmap('plasma').resampled(n_lines)
+
+fig, ax = plt.subplots(layout='constrained')
+
+for i in range(n_lines):
+    ax.plot([0, i], color=cmap(i))
+
+plt.show()
+
+# %%
+# Instead of passing colors one by one to `~.Axes.plot`, we can replace the default
+# color cycle with a different set of colors.  Specifying a `~cycler.cycler` instance
+# within `.rcParams` achieves that.  See :ref:`color_cycle` for details.
+
+
+from cycler import cycler
+
+cmap = mpl.colormaps.get_cmap('Dark2')
+colors = cmap(range(cmap.N))  # cmap.N is number of unique colors in the colormap
+
+with mpl.rc_context({'axes.prop_cycle': cycler(color=colors)}):
+
+    fig, ax = plt.subplots(layout='constrained')
+
+    for i in range(n_lines):
+        ax.plot([0, i])
+
+plt.show()
+
+# %%
+#
+# .. admonition:: References
+#
+#    The use of the following functions, methods, classes and modules is shown
+#    in this example:
+#
+#    - `matplotlib.colors.Colormap`
+#    - `matplotlib.colors.Colormap.resampled`
