Backport PR #23944: FIX: ValueError when hexbin is run with empty arrays and log scaling.

erykoff · meeseeksmachine · commit c6339567de1c · 2022-09-23T04:39:19.000Z
diff --git a/lib/matplotlib/axes/_axes.py b/lib/matplotlib/axes/_axes.py
@@ -4927,7 +4927,9 @@ def reduce_C_function(C: array) -> float
         # autoscale the norm with current accum values if it hasn't been set
         if norm is not None:
             if norm.vmin is None and norm.vmax is None:
-                norm.autoscale(accum)
+                norm.autoscale_None(accum)
+            norm.vmin = np.ma.masked if norm.vmin is None else norm.vmin
+            norm.vmax = np.ma.masked if norm.vmax is None else norm.vmax
 
         if bins is not None:
             if not np.iterable(bins):
diff --git a/lib/matplotlib/tests/test_axes.py b/lib/matplotlib/tests/test_axes.py
@@ -901,6 +901,14 @@ def test_hexbin_empty():
     ax.hexbin([], [])
 
 
+@image_comparison(['hexbin_empty.png'], remove_text=True)
+def test_hexbin_log_empty():
+    # From #23922: creating hexbin with log scaling from empty
+    # dataset raises ValueError
+    ax = plt.gca()
+    ax.hexbin([], [], bins='log')
+
+
 def test_hexbin_pickable():
     # From #1973: Test that picking a hexbin collection works
     fig, ax = plt.subplots()
