[FIX] OWScatterPlotBase: Ignore 'Other' when showing color regions

Orange/widgets/visualize/owscatterplotgraph.py

@@ -43,6 +43,9 @@
 SELECTION_WIDTH = 5
 MAX_N_VALID_SIZE_ANIMATE = 1000
 
+# maximum number of colors (including Other)
+MAX_COLORS = 11
+
 
 class LegendItem(PgLegendItem):
     def __init__(self, size=None, offset=None, pen=None, brush=None):
@@ -1189,7 +1192,9 @@ def update_density(self):
             c_data = self.master.get_color_data()
             if c_data is None:
                 return
-            mask = np.isfinite(self._filter_visible(c_data))
+            visible_c_data = self._filter_visible(c_data)
+            mask = np.bitwise_and(np.isfinite(visible_c_data),
+                                  visible_c_data < MAX_COLORS - 1)
             pens = self.scatterplot_item.data['pen']
             rgb_data = [
                 pen.color().getRgb()[:3] if pen is not None else (255, 255, 255)

Orange/widgets/visualize/tests/test_owscatterplotbase.py

@@ -940,6 +940,46 @@ def test_density_with_missing(self, class_density_image):
         np.testing.assert_equal(y_data, y_data0)
         np.testing.assert_equal(colors, colors0)
 
+    @patch("Orange.widgets.visualize.owscatterplotgraph.MAX_COLORS", 3)
+    @patch("Orange.widgets.utils.classdensity.class_density_image")
+    def test_density_with_max_colors(self, class_density_image):
+        graph = self.graph
+        graph.reset_graph()
+        graph.plot_widget.addItem = Mock()
+        graph.plot_widget.removeItem = Mock()
+
+        graph.class_density = True
+        d = np.arange(10, dtype=float) % 3
+        self.master.get_color_data = lambda: d
+
+        # All colors known
+        graph.update_colors()
+        x_data, y_data, colors = class_density_image.call_args[0][5:]
+        np.testing.assert_equal(x_data, np.arange(10)[d < 2])
+        np.testing.assert_equal(y_data, np.arange(10)[d < 2])
+        self.assertEqual(len(set(colors)), 2)
+
+        # Missing colors
+        d[:3] = np.nan
+        graph.update_colors()
+        x_data, y_data, colors = class_density_image.call_args[0][5:]
+        np.testing.assert_equal(x_data, np.arange(3, 10)[d[3:] < 2])
+        np.testing.assert_equal(y_data, np.arange(3, 10)[d[3:] < 2])
+        self.assertEqual(len(set(colors)), 2)
+
+        # Missing colors + only subsample plotted
+        graph.set_sample_size(8)
+        graph.reset_graph()
+        x_data, y_data, colors = class_density_image.call_args[0][5:]
+        visible_data = graph._filter_visible(d)
+        d_known = np.bitwise_and(np.isfinite(visible_data),
+                                  visible_data < 2)
+        x_data0 = graph._filter_visible(np.arange(10))[d_known]
+        y_data0 = graph._filter_visible(np.arange(10))[d_known]
+        np.testing.assert_equal(x_data, x_data0)
+        np.testing.assert_equal(y_data, y_data0)
+        self.assertLessEqual(len(set(colors)), 2)
+
     def test_labels(self):
         graph = self.graph
         graph.reset_graph()

Orange/widgets/visualize/utils/widget.py

@@ -25,12 +25,12 @@
 from Orange.widgets.utils.plot import OWPlotGUI
 from Orange.widgets.utils.sql import check_sql_input
 from Orange.widgets.utils.state_summary import format_summary_details
-from Orange.widgets.visualize.owscatterplotgraph import OWScatterPlotBase
+from Orange.widgets.visualize.owscatterplotgraph import (
+    OWScatterPlotBase, MAX_COLORS
+)
 from Orange.widgets.visualize.utils.component import OWGraphWithAnchors
 from Orange.widgets.widget import OWWidget, Input, Output, Msg
 
-# maximum number of colors (including Other)
-MAX_COLORS = 11
 
 # maximum number of shapes (including Other)
 MAX_SHAPES = len(OWScatterPlotBase.CurveSymbols) - 1