Remove some direct calls to atleast_1d.

dopplershift · dopplershift · commit 20cb00588bc9 · 2015-07-29T12:04:12.000-05:00
Even if the argument to atleast_1d is array-compatible and has
sufficient dimensions, it is still converted from its original type to a
numpy array. This is overly aggressive for our purposes (especially
unit support), so replace the direct call with a helper function that
only calls atleast_1d if it's actually necessary.
diff --git a/lib/matplotlib/axes/_base.py b/lib/matplotlib/axes/_base.py
@@ -15,7 +15,7 @@
 import matplotlib
 
 from matplotlib import cbook
-from matplotlib.cbook import _string_to_bool
+from matplotlib.cbook import _check_1d, _string_to_bool
 from matplotlib import docstring
 import matplotlib.colors as mcolors
 import matplotlib.lines as mlines
@@ -216,8 +216,10 @@ def _xy_from_xy(self, x, y):
                 if by:
                     y = self.axes.convert_yunits(y)
 
-        x = np.atleast_1d(x)  # like asanyarray, but converts scalar to array
-        y = np.atleast_1d(y)
+        # like asanyarray, but converts scalar to array, and doesn't change
+        # existing compatible sequences
+        x = _check_1d(x)
+        y = _check_1d(y)
         if x.shape[0] != y.shape[0]:
             raise ValueError("x and y must have same first dimension")
         if x.ndim > 2 or y.ndim > 2:
@@ -277,10 +279,10 @@ def _plot_args(self, tup, kwargs):
             if v is not None:
                 kw[k] = v
 
-        y = np.atleast_1d(tup[-1])
+        y = _check_1d(tup[-1])
 
         if len(tup) == 2:
-            x = np.atleast_1d(tup[0])
+            x = _check_1d(tup[0])
         else:
             x = np.arange(y.shape[0], dtype=float)
 
diff --git a/lib/matplotlib/cbook.py b/lib/matplotlib/cbook.py
@@ -2192,6 +2192,21 @@ def is_math_text(s):
     return even_dollars
 
 
+def _check_1d(x):
+    '''
+    Converts a sequence of less than 1 dimension, to an array of 1
+    dimension; leaves everything else untouched.
+    '''
+    if not hasattr(x, 'shape') or len(x.shape) < 1:
+        return np.atleast_1d(x)
+    else:
+        try:
+            x[:, None]
+            return x
+        except (IndexError, TypeError):
+            return np.atleast_1d(x)
+
+
 def _reshape_2D(X):
     """
     Converts a non-empty list or an ndarray of two or fewer dimensions
