Correct error bar cap orientation in polar plots

kyracho · kyracho · commit 62325e9086e8 · 2024-10-01T21:49:45.000Z
diff --git a/lib/matplotlib/axes/_axes.py b/lib/matplotlib/axes/_axes.py
@@ -3766,17 +3766,21 @@ def apply_mask(arrays, mask):
                     caplines[dep_axis].append(mlines.Line2D(
                         x_masked, y_masked, marker=marker, **eb_cap_style))
         if self.name == 'polar':
+            theta_offset = self.get_theta_offset()
+            theta_direction = self.get_theta_direction()
             for axis in caplines:
                 for l in caplines[axis]:
-                    # Rotate caps to be perpendicular to the error bars
                     for theta, r in zip(l.get_xdata(), l.get_ydata()):
-                        rotation = mtransforms.Affine2D().rotate(theta)
+                        adjusted_theta = theta_direction * theta + theta_offset
                         if axis == 'y':
-                            rotation.rotate(-np.pi / 2)
-                        ms = mmarkers.MarkerStyle(marker=marker,
-                                                  transform=rotation)
+                            rotation = (mtransforms.Affine2D()
+                                        .rotate(adjusted_theta - np.pi / 2))
+                        else:
+                            rotation = mtransforms.Affine2D().rotate(adjusted_theta)
+                        ms = mmarkers.MarkerStyle(marker=marker, transform=rotation)
                         self.add_line(mlines.Line2D([theta], [r], marker=ms,
                                                     **eb_cap_style))
+
         else:
             for axis in caplines:
                 for l in caplines[axis]:
diff --git a/lib/matplotlib/tests/baseline_images/test_polar/polar_errorbar.png b/lib/matplotlib/tests/baseline_images/test_polar/polar_errorbar.png
diff --git a/lib/matplotlib/tests/test_polar.py b/lib/matplotlib/tests/test_polar.py
@@ -481,3 +481,16 @@ def test_polar_neg_theta_lims():
     ax.set_thetalim(-np.pi, np.pi)
     labels = [l.get_text() for l in ax.xaxis.get_ticklabels()]
     assert labels == ['-180°', '-135°', '-90°', '-45°', '0°', '45°', '90°', '135°']
+
+
+@image_comparison(baseline_images=['polar_errorbar'], remove_text=True,
+                  extensions=['png'], style='mpl20')
+def test_polar_errorbar():
+    theta = np.arange(0, 2 * np.pi, np.pi / 8)
+    r = theta / np.pi / 2 + 0.5
+
+    fig = plt.figure(figsize=(5, 5))
+    ax = fig.add_subplot(projection='polar')
+    ax.set_theta_zero_location("N")
+    ax.set_theta_direction(-1)
+    ax.errorbar(theta, r, xerr=0.1, yerr=0.1, capsize=7, fmt="o", c="seagreen")
