DOC: explain logscales and imshow (closes #7661)

phobson · phobson · commit 82c4aab0ab5a · 2017-01-11T11:11:16.000-08:00
diff --git a/doc/users/whats_new/imshow_logscales.rst b/doc/users/whats_new/imshow_logscales.rst
@@ -0,0 +1,35 @@
+Non-linears scales on image plots
+---------------------------------
+
+:func:`imshow` now draws data at the requested points in data space after the
+application of non-linear scales.
+
+The image on the left demonstrates the new, correct behavior.
+The old behavior can be recreated using :func:`pcolormesh` as
+demonstrated on the right.
+
+Example
+```````
+::
+
+    import numpy as np
+    import matplotlib.pyplot as plt
+
+    data = np.arange(30).reshape(5, 6)
+    x = np.linspace(0, 6, 7)
+    y = 10**np.linspace(0, 5, 6)
+    X, Y = np.meshgrid(x, y)
+
+    fig, (ax1, ax2) = plt.subplots(ncols=2, figsize=(8, 4))
+
+    ax1.imshow(data, aspect="auto", extent=(0, 5, 1e0, 1e5), interpolation='nearest')
+    ax1.set_yscale('log')
+    ax1.set_title('Using ax.imshow')
+
+    ax2.pcolormesh(x, y, np.flipud(data))
+    ax2.set_yscale('log')
+    ax2.set_title('Using ax.pcolormesh')
+    ax2.autoscale('tight')
+
+    plt.show()
+
