Merge pull request matplotlib#15140 from dstansby/mask-fmt

FIX: ScalarFormatter formatting of masked values

Author: tacaswell

lib/matplotlib/tests/test_image.py

@@ -1103,3 +1103,18 @@ def test_respects_bbox():
     buf_after = io.BytesIO()
     fig.savefig(buf_after, format="rgba")
     assert buf_before.getvalue() != buf_after.getvalue()  # Not all white.
+
+
+def test_image_cursor_formatting():
+    fig, ax = plt.subplots()
+    # Create a dummy image to be able to call format_cursor_data
+    im = ax.imshow(np.zeros((4, 4)))
+
+    data = np.ma.masked_array([0], mask=[True])
+    assert im.format_cursor_data(data) == '[]'
+
+    data = np.ma.masked_array([0], mask=[False])
+    assert im.format_cursor_data(data) == '[0]'
+
+    data = np.nan
+    assert im.format_cursor_data(data) == '[nan]'

lib/matplotlib/ticker.py

@@ -629,6 +629,8 @@ def format_data_short(self, value):
         """
         if self._useLocale:
             return locale.format_string('%-12g', (value,))
+        elif isinstance(value, np.ma.MaskedArray) and value.mask:
+            return ''
         else:
             return '%-12g' % value