Avoid overwritting by copying motion vec

navipy/moving/maths.py

@@ -41,9 +41,9 @@ def next_pos(motion_vec, move_mode, move_param=None):
                                       names=['position',
                                              'orientation'])
     speed = pd.Series(index=index)
-    speed['location']['dx'] = motion_vec['location']['dx']
-    speed['location']['dy'] = motion_vec['location']['dy']
-    speed['location']['dz'] = motion_vec['location']['dz']
+    speed.loc[('location', 'dx')] = motion_vec[('location', 'dx')]
+    speed.loc[('location', 'dy')] = motion_vec[('location', 'dy')]
+    speed.loc[('location', 'dz')] = motion_vec[('location', 'dz')]
     # speed = motion_vec.loc[['dx', 'dy', 'dz']]
     if move_mode == 'on_cubic_grid':
         # speed in spherical coord
@@ -87,7 +87,7 @@ def next_pos(motion_vec, move_mode, move_param=None):
         # scaling = 1  # <=> dt = 1, user need to scale speed in dt units
     else:
         raise ValueError('grid_mode is not supported')
-    toreturn = motion_vec
+    toreturn = motion_vec.copy()
     toreturn.loc[('location', 'x')] += speed['location']['dx']
     toreturn.loc[('location', 'y')] += speed['location']['dy']
     toreturn.loc[('location', 'z')] += speed['location']['dz']