[Behavior change] Remove zero division error for linear_transform

kwave/utils/math.py

@@ -386,11 +386,12 @@ def compute_linear_transform(pos1, pos2, offset=None):
 
     magnitude = np.linalg.norm(beam_vec)
 
-    # TODO: it seems matlab behaviour is to return nans when positions are the same.
-    #       we should open an issue and change our behaviour once matlab is fixed.
-    # if magnitude == 0:
-    #     # "pos1 and pos2 are the same"
-    #     return np.eye(3), 0 if offset is None else offset
+    #  matlab behaviour is to return nans when positions are the same.
+    #  we choose to return the identity matrix and the offset in this case.
+    #  TODO: we should open an issue and change our behaviour once matlab is fixed.
+    if magnitude == 0:
+        # "pos1 and pos2 are the same"
+        return np.eye(3), 0 if offset is None else offset
 
     # Normalise to give unit beam vector
     beam_vec = beam_vec / magnitude

tests/matlab_test_data_collectors/python_testers/computeLinearTransform_test.py

@@ -17,14 +17,21 @@ def test_compute_linear_transform():
         if len(params) == 2:
             pos1, pos2 = params
             pos1, pos2 = pos1.astype(float), pos2.astype(float)
+
             rot_mat, offset_pos = compute_linear_transform(pos1, pos2)
+
         else:
             pos1, pos2, offset = params
             pos1, pos2, offset = pos1.astype(float), pos2.astype(float), float(offset)
             rot_mat, offset_pos = compute_linear_transform(pos1, pos2, offset)
 
-        assert np.allclose(rot_mat, reader.expected_value_of("rotMat"), equal_nan=True)
-        assert np.allclose(offset_pos, reader.expected_value_of("offsetPos"), equal_nan=True)
+        if not np.any(np.isnan(reader.expected_value_of("rotMat"))):
+            assert np.allclose(rot_mat, reader.expected_value_of("rotMat"))
+            assert np.allclose(offset_pos, reader.expected_value_of("offsetPos"))
         reader.increment()
 
     logging.log(logging.INFO, "compute_linear_transform(..) works as expected!")
+
+
+if __name__ == "__main__":
+    test_compute_linear_transform()