MAINT: Extract helper function to cbook

eric-wieser · eric-wieser · commit ac8f801624e7 · 2018-03-17T18:25:45.000-07:00
diff --git a/lib/matplotlib/cbook/__init__.py b/lib/matplotlib/cbook/__init__.py
@@ -2067,3 +2067,42 @@ def method(self, *args, **kwargs):
         raise NotImplementedError("Parent class already defines aliases")
     cls._alias_map = alias_d
     return cls
+
+
+def _array_perimeter(arr):
+    """
+    Get the elements on the perimeter of ``arr``,
+
+    Parameters
+    ----------
+    arr : ndarray, shape (M, N)
+        The input array
+
+    Returns
+    -------
+    perimeter : ndarray, shape (2*(M - 1) + 2*(N - 1),)
+        The elements on the perimeter of the array::
+
+            [arr[0,0] ... arr[0,-1] ... arr[-1, -1] ... arr[-1,0] ...]
+
+    Examples
+    --------
+    >>> i, j = np.ogrid[:3,:4]
+    >>> a = i*10 + j
+    >>> a
+    array([[ 0,  1,  2,  3],
+           [10, 11, 12, 13],
+           [20, 21, 22, 23]])
+    >>> _array_perimeter(arr)
+    array([ 0,  1,  2,  3, 13, 23, 22, 21, 20, 10])
+    """
+    # note we use Python's half-open ranges to avoid repeating
+    # the corners
+    forward = np.s_[0:-1]      # [0 ... -1)
+    backward = np.s_[-1:0:-1]  # [-1 ... 0)
+    return np.concatenate((
+        arr[0, forward],
+        arr[forward, -1],
+        arr[-1, backward],
+        arr[backward, 0],
+    ))
diff --git a/lib/mpl_toolkits/mplot3d/axes3d.py b/lib/mpl_toolkits/mplot3d/axes3d.py
@@ -1684,25 +1684,6 @@ def plot_surface(self, X, Y, Z, *args, **kwargs):
         if shade and cmap is not None and fcolors is not None:
             fcolors = self._shade_colors_lightsource(Z, cmap, lightsource)
 
-        def boundary_edge(arr):
-            """
-            Get the boundary elements of the rectangle ``arr``,
-
-                [arr[0,0] ... arr[0,-1] ... arr[-1, -1] ... arr[-1,0] ...]
-
-            If arr.shape is (M, N), the result is of length 2(N+M-2)
-            """
-            # note we use Python's half-open ranges to avoid repeating
-            # the corners
-            forward = np.s_[0:-1]      # [0 ... -1)
-            backward = np.s_[-1:0:-1]  # [-1 ... 0)
-            return np.concatenate((
-                arr[0, forward],
-                arr[forward, -1],
-                arr[-1, backward],
-                arr[backward, 0],
-            ))
-
         # evenly spaced, and including both endpoints
         row_inds = list(range(0, rows-1, rstride)) + [rows-1]
         col_inds = list(range(0, cols-1, cstride)) + [cols-1]
@@ -1713,7 +1694,7 @@ def boundary_edge(arr):
             for cs, cs_next in zip(col_inds[:-1], col_inds[1:]):
                 ps = [
                     # +1 ensures we share edges between polygons
-                    boundary_edge(a[rs:rs_next+1, cs:cs_next+1])
+                    cbook._array_perimeter(a[rs:rs_next+1, cs:cs_next+1])
                     for a in (X, Y, Z)
                 ]
                 # ps = np.stack(ps, axis=-1)
