Code comments

Author: scottshambaugh

lib/matplotlib/collections.py

@@ -1511,13 +1511,13 @@ def _make_verts(self, t, f1, f2, where):
         t, f1, f2 = np.broadcast_arrays(np.atleast_1d(t), f1, f2, subok=True)
 
         self._bbox = transforms.Bbox.null()
-        t_w = t.data[where] if np.ma.isMA(t) else t[where]
-        n = len(t_w)
+        t_where = t.data[where] if np.ma.isMA(t) else t[where]
+        n = len(t_where)
         if n > 0:
-            pts = np.empty((2 * n, 2))
-            pts[:n, 0] = t_w
+            pts = np.empty((2 * n, 2))  # Preallocate and fill for speed
+            pts[:n, 0] = t_where
             pts[:n, 1] = f1.data[where] if np.ma.isMA(f1) else f1[where]
-            pts[n:, 0] = t_w
+            pts[n:, 0] = t_where
             pts[n:, 1] = f2.data[where] if np.ma.isMA(f2) else f2[where]
             self._bbox.update_from_data_xy(self._fix_pts_xy_order(pts))
 

lib/matplotlib/lines.py

@@ -714,6 +714,7 @@ def recache(self, always=False):
             vertices = self._xy
         else:
             steps = step_func(*self._xy.T)
+            # Preallocate and fill for speed
             vertices = np.empty((steps.shape[1], 2))
             vertices[:, 0] = steps[0]
             vertices[:, 1] = steps[1]
@@ -735,6 +736,7 @@ def _transform_path(self, subslice=None):
                 vertices = self._xy[subslice]
             else:
                 steps = step_func(*self._xy[subslice, :].T)
+                # Preallocate and fill for speed
                 vertices = np.empty((steps.shape[1], 2))
                 vertices[:, 0] = steps[0]
                 vertices[:, 1] = steps[1]

lib/matplotlib/transforms.py

@@ -909,7 +909,7 @@ def update_from_path(self, path, ignore=None, updatex=True, updatey=True):
             minx = np.min(x, initial=np.inf)
             points[0, 0] = min(points[0, 0], minx)
             points[1, 0] = max(points[1, 0], np.max(x, initial=-np.inf))
-            if minx > 0:
+            if minx > 0:  # Fast path for all-positive x values
                 minpos[0] = min(minpos[0], minx)
             else:
                 minpos[0] = min(minpos[0], np.min(x[x > 0], initial=np.inf))
@@ -918,7 +918,7 @@ def update_from_path(self, path, ignore=None, updatex=True, updatey=True):
             miny = np.min(y, initial=np.inf)
             points[0, 1] = min(points[0, 1], miny)
             points[1, 1] = max(points[1, 1], np.max(y, initial=-np.inf))
-            if miny > 0:
+            if miny > 0:  # Fast path for all-positive y values
                 minpos[1] = min(minpos[1], miny)
             else:
                 minpos[1] = min(minpos[1], np.min(y[y > 0], initial=np.inf))