Merge pull request #404 from keflavich/clearer_warp_example

Slight change to warp_coords docstring

skimage/transform/_geometric.py

@@ -849,6 +849,8 @@ def warp_coords(coord_map, shape, dtype=np.float64):
     ----------
     coord_map : callable like GeometricTransform.inverse
         Return input coordinates for given output coordinates.
+        Coordinates are in the shape (P,2), where P is the number
+        of coordinates and each element is an x,y pair
     shape : tuple
         Shape of output image ``(rows, cols[, bands])``.
     dtype : np.dtype or string
@@ -875,18 +877,18 @@ def warp_coords(coord_map, shape, dtype=np.float64):
 
     Examples
     --------
-    Produce a coordinate map that Shifts an image to the right:
+    Produce a coordinate map that Shifts an image up and to the right:
 
     >>> from skimage import data
     >>> from scipy.ndimage import map_coordinates
     >>>
-    >>> def shift_right(xy):
-    ...     xy[:, 0] -= 10
-    ...     return xy
+    >>> def shift_up10_left20(xy):
+    ...     return xy-np.array([-20,10])[None,:]
     >>>
     >>> image = data.lena().astype(np.float32)
-    >>> coords = warp_coords(shift_right, image.shape)
+    >>> coords = warp_coords(shift_up10_left20, image.shape)
     >>> warped_image = map_coordinates(image, coords)
+    >>>
 
     """
     rows, cols = shape[0], shape[1]