Added check for complex eignevalues or eigenvectors in uncertainity, …

…plus added tests for it

stonesoup/plotter.py

@@ -343,6 +343,10 @@ def plot_tracks(self, tracks, mapping, uncertainty=False, particle=False, track_
                     HH = np.eye(track.ndim)[mapping, :]  # Get position mapping matrix
                     for state in track:
                         w, v = np.linalg.eig(HH @ state.covar @ HH.T)
+                        if np.iscomplexobj(w) or np.iscomplexobj(v):
+                            warnings.warn("Can not plot uncertainty for all states due to complex "
+                                          "eignevalues or eigenvectors", UserWarning)
+                            continue
                         max_ind = np.argmax(w)
                         min_ind = np.argmin(w)
                         orient = np.arctan2(v[1, max_ind], v[0, max_ind])

stonesoup/tests/test_plotter.py

@@ -196,3 +196,16 @@ def test_plot_density_equal_x_y():
             timestamp=start_time + timedelta(seconds=k + 1)))
     with pytest.raises(ValueError):
         plotter.plot_density({truth}, index=None)
+
+
+def test_plot_complex_uncertainty():
+    plotter = Plotter()
+    track = Track([
+        GaussianState(
+            state_vector=[0, 0],
+            covar=[[10, -1], [1, 10]])
+    ])
+    with pytest.warns(UserWarning, match="Can not plot uncertainty for all states due to complex "
+                                         "eignevalues or eigenvectors"):
+
+        plotter.plot_tracks(track, mapping=[0, 1], uncertainty=True)