matplotlib · dstansby · May 29, 2017 · May 9, 2017 · May 9, 2017 · May 11, 2017
diff --git a/examples/api/colorbar_only.py b/examples/api/colorbar_only.py
diff --git a/tutorials/colors/colorbar_only.py b/tutorials/colors/colorbar_only.py
@@ -0,0 +1,108 @@
+"""
+=============================
+Customized Colorbars Tutorial
+=============================
+
+This tutorial shows how to build colorbars without an attached plot.
+
+Customized Colorbars
+====================
+
+:class:`~matplotlib.colorbar.ColorbarBase` derives from
+:mod:`~matplotlib.cm.ScalarMappable` and puts a colorbar in a specified axes,
+so it has everything needed for a standalone colorbar. It can be used as is to
+make a colorbar for a given colormap and does not need a mappable object like
+an image. In this tutorial we will explore what can be done with standalone
+colorbar.
+
+We will start by making a figure of desired size and adding three axes.
+"""
+
+import matplotlib.pyplot as plt
+import matplotlib as mpl
+
+fig, (ax1, ax2, ax3) = plt.subplots(nrows=3)
+
+###############################################################################
+# Basic continuous colorbar
+# -------------------------
+#
+# Set the colormap and norm to correspond to the data for which the colorbar
+# will be used. Then create the colorbar by calling
+# :class:`~matplotlib.colorbar.ColorbarBase` and specify axis, colormap, norm
+# and orientation as parameters. Here we create a basic continuous colorbar
+# with ticks and labels. More information on colorbar api can be found
+# `here <https://matplotlib.org/api/colorbar_api.html>`.
+
+cmap = mpl.cm.cool
+norm = mpl.colors.Normalize(vmin=5, vmax=10)
+
+cb1 = mpl.colorbar.ColorbarBase(ax1, cmap=cmap,
+                                norm=norm,
+                                orientation='horizontal')
+cb1.set_label('Some Units')
+
+###############################################################################
+# Discrete intervals colorbar
+# ---------------------------
+#
+# The second example illustrates the use of a
+# :class:`~matplotlib.colors.ListedColormap` which generates a colormap from a
+# set of listed colors, :func:`colors.BoundaryNorm` which generates a colormap
+# index based on discrete intervals and extended ends to show the "over" and
+# "under" value colors. Over and under are used to display data outside of the
+# normalized [0,1] range. Here we pass colors as gray shades as a string
+# encoding a float in the 0-1 range.
+#
+# If a :class:`~matplotlib.colors.ListedColormap` is used, the length of the
+# bounds array must be one greater than the length of the color list. The
+# bounds must be monotonically increasing.
+#
+# This time we pass some more arguments in addition to previous arguments to
+# :class:`~matplotlib.colorbar.ColorbarBase`. For the out-of-range values to
+# display on the colorbar, we have to use the *extend* keyword argument. To use
+# *extend*, you must specify two extra boundaries. Finally spacing argument
+# ensures that intervals are shown on colorbar proportionally.
+
+cmap = mpl.colors.ListedColormap(['red', 'green', 'blue', 'cyan'])
+cmap.set_over('0.25')
+cmap.set_under('0.75')
+
+bounds = [1, 2, 4, 7, 8]
+norm = mpl.colors.BoundaryNorm(bounds, cmap.N)
+cb2 = mpl.colorbar.ColorbarBase(ax2, cmap=cmap,
+                                norm=norm,
+                                boundaries=[0] + bounds + [13],
+                                extend='both',
+                                ticks=bounds,
+                                spacing='proportional',
+                                orientation='horizontal')
+cb2.set_label('Discrete intervals, some other units')
+
+###############################################################################
+# Colorbar with custom extension lengths
+# --------------------------------------
+#
+# Here we illustrate the use of custom length colorbar extensions, used on a
+# colorbar with discrete intervals. To make the length of each extension same
+# as the length of the interior colors, use ``extendfrac='auto'``.
+
+cmap = mpl.colors.ListedColormap(['royalblue', 'cyan',
+                                  'yellow', 'orange'])
+cmap.set_over('red')
+cmap.set_under('blue')
+
+bounds = [-1.0, -0.5, 0.0, 0.5, 1.0]
+norm = mpl.colors.BoundaryNorm(bounds, cmap.N)
+cb3 = mpl.colorbar.ColorbarBase(ax3, cmap=cmap,
+                                norm=norm,
+                                boundaries=[-10] + bounds + [10],
+                                extend='both',
+                                extendfrac='auto',
+                                ticks=bounds,
+                                spacing='uniform',
+                                orientation='horizontal')
+cb3.set_label('Custom extension lengths, some other units')
+
+plt.tight_layout()
+plt.show()