Backport PR #16300: Don't default to negative radii in polar plot.

jklymak · meeseeksmachine · commit 47479b04b671 · 2020-01-23T17:23:18.000Z
diff --git a/lib/matplotlib/projections/polar.py b/lib/matplotlib/projections/polar.py
@@ -398,6 +398,7 @@ class RadialLocator(mticker.Locator):
     :class:`~matplotlib.ticker.Locator` (which may be different
     depending on the scale of the *r*-axis.
     """
+
     def __init__(self, base, axes=None):
         self.base = base
         self._axes = axes
@@ -429,6 +430,11 @@ def refresh(self):
         # docstring inherited
         return self.base.refresh()
 
+    def nonsingular(self, vmin, vmax):
+        # docstring inherited
+        return ((0, 1) if (vmin, vmax) == (-np.inf, np.inf)  # Init. limits.
+                else self.base.nonsingular(vmin, vmax))
+
     def view_limits(self, vmin, vmax):
         vmin, vmax = self.base.view_limits(vmin, vmax)
         if vmax > vmin:
diff --git a/lib/matplotlib/tests/test_axes.py b/lib/matplotlib/tests/test_axes.py
@@ -2211,6 +2211,17 @@ def test_log_scales_invalid():
         ax.set_ylim(-1, 10)
 
 
+def test_polar_no_data():
+    plt.subplot(projection="polar")
+    ax = plt.gca()
+    assert ax.get_rmin() == 0 and ax.get_rmax() == 1
+    plt.close("all")
+    # Used to behave differently (by triggering an autoscale with no data).
+    plt.polar()
+    ax = plt.gca()
+    assert ax.get_rmin() == 0 and ax.get_rmax() == 1
+
+
 @image_comparison(['stackplot_test_image', 'stackplot_test_image'])
 def test_stackplot():
     fig = plt.figure()
