SOM: Fix crash when color is constant

Author: janezd

Orange/widgets/unsupervised/owsom.py

@@ -833,6 +833,17 @@ def set_color_bins(self):
                 binning = decimal_binnings(col, min_bins=4)[-1]
             self.thresholds = binning.thresholds[1:-1]
             self.bin_labels = (binning.labels[1:-1], binning.short_labels[1:-1])
+            if not self.bin_labels[0] and binning.labels:
+                # Nan's are already filtered out, but it doesn't hurt much
+                # to use nanmax/nanmin
+                if np.nanmin(col) == np.nanmax(col):
+                    # Handle a degenerate case with a single value
+                    # Use the second threshold (because value must be smaller),
+                    # but the first threshold as label (because that's the
+                    # actual value in the data.
+                    self.thresholds = binning.thresholds[1:]
+                    self.bin_labels = (binning.labels[:1],
+                                       binning.short_labels[:1])
             palette = BinnedContinuousPalette.from_palette(
                 self.attr_color.palette, binning.thresholds)
             self.colors = palette
@@ -871,6 +882,8 @@ def create_legend(self):
 
     def _bin_names(self):
         labels, short_labels = self.bin_labels
+        if len(labels) <= 1:
+            return labels
         return \
             [f"< {labels[0]}"] \
             + [f"{x} - {y}" for x, y in zip(labels, short_labels[1:])] \

Orange/widgets/unsupervised/tests/test_owsom.py

@@ -8,6 +8,7 @@
 
 from Orange.data import Table, Domain
 from Orange.widgets.tests.base import WidgetTest
+from Orange.widgets.tests.utils import simulate
 from Orange.widgets.utils.annotated_data import ANNOTATED_DATA_FEATURE_NAME
 from Orange.widgets.unsupervised.owsom import OWSOM, SomView, SOM
 
@@ -220,6 +221,14 @@ def test_attr_color_change(self):
         self.assertIsNotNone(widget.thresholds)
         widget._redraw.assert_called()
 
+    def test_colored_circles_with_constant(self):
+        with self.iris.unlocked():
+            self.iris.X[:, 0] = 1
+        self.send_signal(self.widget.Inputs.data, self.iris)
+        combo = self.widget.controls.attr_color
+        simulate.combobox_activate_index(
+            combo, combo.model().indexOf(self.iris.domain.attributes[0]))
+
     @_patch_recompute_som
     def test_cell_sizes(self):
         widget = self.widget