owlinearprojection: Add class to effective_data to fix LDA.

Author: lanzagar

Orange/widgets/visualize/owlinearprojection.py

@@ -329,7 +329,8 @@ def effective_variables(self):
 
     @property
     def effective_data(self):
-        return self.data.transform(Domain(self.effective_variables))
+        return self.data.transform(Domain(self.effective_variables,
+                                          self.data.domain.class_vars))
 
     def __vizrank_set_attrs(self, attrs):
         if not attrs:

Orange/widgets/visualize/tests/test_owlinearprojection.py

@@ -85,6 +85,8 @@ def test_no_data_for_lda(self):
         self.send_signal(self.widget.Inputs.data, self.data)
         self.widget.radio_placement.buttons[Placement.LDA].click()
         self.assertTrue(buttons[Placement.LDA].isEnabled())
+        output = self.get_output(self.widget.Outputs.components)
+        self.assertTrue(output and len(output) == 2)
         self.send_signal(self.widget.Inputs.data, Table("housing"))
         self.assertFalse(buttons[Placement.LDA].isEnabled())
         self.send_signal(self.widget.Inputs.data, None)