Merge pull request biolab#2014 from jerneju/keyerror-mosaic

[FIX] Handle KeyError Mosaic Display (owmosaic.py)
(cherry picked from commit 682a939)

Author: astaric

Orange/widgets/visualize/owmosaic.py

@@ -404,7 +404,7 @@ def set_data(self, data):
             self.discrete_data = None
         elif any(attr.is_continuous for attr in data.domain):
             self.discrete_data = Discretize(
-                method=EqualFreq(n=4), discretize_classes=True,
+                method=EqualFreq(n=4), remove_const=False, discretize_classes=True,
                 discretize_metas=True)(data)
         else:
             self.discrete_data = self.data

Orange/widgets/visualize/tests/test_owmosaic.py

@@ -53,6 +53,14 @@ def test_missing_values(self):
         data = Table(Domain(attrs, class_var), X, np.array([np.nan] * 6))
         self.send_signal("Data", data)
 
+    def test_keyerror(self):
+        """gh-2014
+        Check if it works when a table has only one row or duplicates.
+        Discretizer must have remove_const set to False.
+        """
+        data = Table("iris")
+        data = data[0:1]
+        self.send_signal("Data", data)
 
 # Derive from WidgetTest to simplify creation of the Mosaic widget, although
 # we are actually testing the MosaicVizRank dialog and not the widget