Merge pull request matplotlib#27818 from dstansby/log-hexbin-offsets

Set polygon offsets for log scaled hexbin

Author: ksunden

lib/matplotlib/axes/_axes.py

@@ -5028,7 +5028,7 @@ def hexbin(self, x, y, C=None, gridsize=100, bins=None,
             A `.PolyCollection` defining the hexagonal bins.
 
             - `.PolyCollection.get_offsets` contains a Mx2 array containing
-              the x, y positions of the M hexagon centers.
+              the x, y positions of the M hexagon centers in data coordinates.
             - `.PolyCollection.get_array` contains the values of the M
               hexagons.
 
@@ -5206,7 +5206,7 @@ def reduce_C_function(C: array) -> float
             linewidths = [mpl.rcParams['patch.linewidth']]
 
         if xscale == 'log' or yscale == 'log':
-            polygons = np.expand_dims(polygon, 0) + np.expand_dims(offsets, 1)
+            polygons = np.expand_dims(polygon, 0)
             if xscale == 'log':
                 polygons[:, :, 0] = 10.0 ** polygons[:, :, 0]
                 xmin = 10.0 ** xmin
@@ -5217,20 +5217,16 @@ def reduce_C_function(C: array) -> float
                 ymin = 10.0 ** ymin
                 ymax = 10.0 ** ymax
                 self.set_yscale(yscale)
-            collection = mcoll.PolyCollection(
-                polygons,
-                edgecolors=edgecolors,
-                linewidths=linewidths,
-                )
         else:
-            collection = mcoll.PolyCollection(
-                [polygon],
-                edgecolors=edgecolors,
-                linewidths=linewidths,
-                offsets=offsets,
-                offset_transform=mtransforms.AffineDeltaTransform(
-                    self.transData),
-            )
+            polygons = [polygon]
+
+        collection = mcoll.PolyCollection(
+            polygons,
+            edgecolors=edgecolors,
+            linewidths=linewidths,
+            offsets=offsets,
+            offset_transform=mtransforms.AffineDeltaTransform(self.transData)
+        )
 
         # Set normalizer if bins is 'log'
         if cbook._str_equal(bins, 'log'):

lib/matplotlib/tests/test_axes.py

@@ -1020,6 +1020,27 @@ def test_hexbin_log():
                   marginals=True, reduce_C_function=np.sum)
     plt.colorbar(h)
 
+    # Make sure offsets are set
+    assert h.get_offsets().shape == (11558, 2)
+
+
+def test_hexbin_log_offsets():
+    x = np.geomspace(1, 100, 500)
+
+    fig, ax = plt.subplots()
+    h = ax.hexbin(x, x, xscale='log', yscale='log', gridsize=2)
+    np.testing.assert_almost_equal(
+        h.get_offsets(),
+        np.array(
+            [[0, 0],
+             [0, 2],
+             [1, 0],
+             [1, 2],
+             [2, 0],
+             [2, 2],
+             [0.5, 1],
+             [1.5, 1]]))
+
 
 @image_comparison(["hexbin_linear.png"], style="mpl20", remove_text=True)
 def test_hexbin_linear():