fix crash in shifted_exyz

gridlock/grid.py

@@ -139,7 +139,7 @@ class Grid(object):
         # If shift is negative, use left cell's dx to determine shift
         for a in range(3):
             if shifts[a] < 0:
-                dxyz[a] = numpy.roll(dxyz, 1)
+                dxyz[a] = numpy.roll(dxyz[a], 1)
 
         return [self.exyz[a] + dxyz[a] * shifts[a] for a in range(3)]
 

gridlock/position.py

@@ -99,7 +99,7 @@ def pos2ind(self,
             x = self.shifted_xyz(which_shifts)[a][xi]
             dx = self.shifted_dxyz(which_shifts)[a][xi]
             f = (r[a] - x) / dx
-            
+
             # Clip to centers
             grid_pos[a] = numpy.clip(xi + f, 0, self.shape[a] - 1)
     return grid_pos