Merge pull request #10705 from JelsB/bug-fix-for-issue-7942

timhoffm · web-flow · commit 95497a61b693 · 2018-03-16T01:53:31.000+01:00
FIX: enable extend kwargs with log scale colorbar
diff --git a/examples/images_contours_and_fields/contourf_log.py b/examples/images_contours_and_fields/contourf_log.py
@@ -42,9 +42,7 @@
 # lev_exp = np.arange(np.floor(np.log10(z.min())-1),
 #                    np.ceil(np.log10(z.max())+1))
 # levs = np.power(10, lev_exp)
-# cs = P.contourf(X, Y, z, levs, norm=colors.LogNorm())
-
-# The 'extend' kwarg does not work yet with a log scale.
+# cs = ax.contourf(X, Y, z, levs, norm=colors.LogNorm())
 
 cbar = fig.colorbar(cs)
 
diff --git a/lib/matplotlib/contour.py b/lib/matplotlib/contour.py
@@ -823,9 +823,6 @@ def __init__(self, ax, *args, **kwargs):
             self.logscale = True
             if norm is None:
                 norm = colors.LogNorm()
-            if self.extend is not 'neither':
-                raise ValueError('extend kwarg does not work yet with log '
-                                 ' scale')
         else:
             self.logscale = False
 
@@ -1206,7 +1203,10 @@ def _process_levels(self):
         # ...except that extended layers must be outside the
         # normed range:
         if self.extend in ('both', 'min'):
-            self.layers[0] = -1e150
+            if self.logscale:
+                self.layers[0] = 1e-150
+            else:
+                self.layers[0] = -1e150
         if self.extend in ('both', 'max'):
             self.layers[-1] = 1e150
 
diff --git a/lib/matplotlib/tests/baseline_images/test_contour/contour_log_extension.png b/lib/matplotlib/tests/baseline_images/test_contour/contour_log_extension.png
diff --git a/lib/matplotlib/tests/test_contour.py b/lib/matplotlib/tests/test_contour.py
@@ -6,6 +6,7 @@
 from matplotlib.testing.decorators import image_comparison
 from matplotlib import pyplot as plt
 from numpy.testing import assert_array_almost_equal
+from matplotlib.colors import LogNorm
 import pytest
 import warnings
 
@@ -367,3 +368,36 @@ def test_circular_contour_warning():
         cs = plt.contour(x, y, r)
         plt.clabel(cs)
     assert len(record) == 0
+
+
+@image_comparison(baseline_images=['contour_log_extension'],
+                  extensions=['png'], remove_text=True, style='mpl20')
+def test_contourf_log_extension():
+    # Test that contourf with lognorm is extended correctly
+    fig = plt.figure(figsize=(10, 5))
+    fig.subplots_adjust(left=0.05, right=0.95)
+    ax1 = fig.add_subplot(131)
+    ax2 = fig.add_subplot(132)
+    ax3 = fig.add_subplot(133)
+
+    # make data set with large range e.g. between 1e-8 and 1e10
+    data_exp = np.linspace(-8, 10, 1200)
+    data = np.power(10, data_exp).reshape(30, 40)
+    # make manual levels e.g. between 1e-4 and 1e-6
+    levels_exp = np.arange(-4., 7.)
+    levels = np.power(10., levels_exp)
+
+    # original data
+    c1 = ax1.contourf(data,
+                      norm=LogNorm(vmin=data.min(), vmax=data.max()))
+    # just show data in levels
+    c2 = ax2.contourf(data, levels=levels,
+                      norm=LogNorm(vmin=levels.min(), vmax=levels.max()),
+                      extend='neither')
+    # extend data from levels
+    c3 = ax3.contourf(data, levels=levels,
+                      norm=LogNorm(vmin=levels.min(), vmax=levels.max()),
+                      extend='both')
+    plt.colorbar(c1, ax=ax1)
+    plt.colorbar(c2, ax=ax2)
+    plt.colorbar(c3, ax=ax3)
