BUG: Fix implementation of _is_closed_polygon

dopplershift · dopplershift · commit efa5b101ed84 · 2020-06-30T12:37:23.000-06:00
It's a bad idea to use floating point equality to check if two points
are equal. While not a huge difference, especially in the case of
contour analysis, this was causing testing issues downstream. In one
case this yielded different results for the same test on different OSes.
diff --git a/lib/matplotlib/contour.py b/lib/matplotlib/contour.py
@@ -629,7 +629,7 @@ def _is_closed_polygon(X):
     presumably coordinates on a polygonal curve, in which case this function
     tests if that curve is closed.
     """
-    return np.all(X[0] == X[-1])
+    return np.allclose(X[0], X[-1], rtol=1e-10, atol=1e-13)
 
 
 def _find_closest_point_on_path(lc, point):
