Merge pull request matplotlib#2846 from neggert/hist_step_horiz_bugfix

Fix bug in horizontal step histograms (matplotlib#2830)

Author: tacaswell

lib/matplotlib/axes.py

@@ -8494,10 +8494,11 @@ def hist(self, x, bins=10, range=None, normed=False, weights=None,
                 if log:
                     y[y < minimum] = minimum
                 if orientation == 'horizontal':
-                    x, y = y, x
-
-                xvals.append(x.copy())
-                yvals.append(y.copy())
+                    xvals.append(y.copy())
+                    yvals.append(x.copy())
+                else:
+                    xvals.append(x.copy())
+                    yvals.append(y.copy())
 
             if fill:
                 # add patches in reverse order so that when stacking,

lib/matplotlib/tests/baseline_images/test_axes/hist_step_horiz.png

@@ -1088,6 +1088,16 @@ def test_hist_step():
     ax.set_xlim(-1, 5)
 
 
+@image_comparison(baseline_images=['hist_step_horiz'], extensions=['png'])
+def test_hist_step_horiz():
+    # make some data
+    d1 = np.linspace(0, 10, 50)
+    d2 = np.linspace(1, 3, 20)
+    fig = plt.figure()
+    ax = fig.add_subplot(111)
+    ax.hist( (d1, d2), histtype="step", orientation="horizontal")
+
+
 @image_comparison(baseline_images=['hist_stacked_weights'])
 def test_hist_stacked_weighted():
     # make some data