BUG: Fix fill_between(x) with decreasing data (Fixes #9235)

dopplershift · dopplershift · commit e6a115c936e4 · 2017-09-26T14:26:57.000-06:00
One of the calls to interp passes data which is not guaranteed to be in
increasing order, which interp requires. Just use argsort the data, like
is done above.
diff --git a/lib/matplotlib/axes/_axes.py b/lib/matplotlib/axes/_axes.py
@@ -4876,7 +4876,9 @@ def get_interp_point(ind):
                     diff_order = diff_values.argsort()
                     diff_root_x = np.interp(
                         0, diff_values[diff_order], x_values[diff_order])
-                    diff_root_y = np.interp(diff_root_x, x_values, y1_values)
+                    x_order = x_values.argsort()
+                    diff_root_y = np.interp(diff_root_x, x_values[x_order],
+                                            y1_values[x_order])
                     return diff_root_x, diff_root_y
 
                 start = get_interp_point(ind0)
@@ -5026,7 +5028,9 @@ def get_interp_point(ind):
                     diff_order = diff_values.argsort()
                     diff_root_y = np.interp(
                         0, diff_values[diff_order], y_values[diff_order])
-                    diff_root_x = np.interp(diff_root_y, y_values, x1_values)
+                    y_order = y_values.argsort()
+                    diff_root_x = np.interp(diff_root_y, y_values[y_order],
+                                            x1_values[y_order])
                     return diff_root_x, diff_root_y
 
                 start = get_interp_point(ind0)
