matplotlib · tacaswell · Nov 23, 2013 · Aug 14, 2013
diff --git a/lib/matplotlib/axes.py b/lib/matplotlib/axes.py
@@ -8319,18 +8319,18 @@ def hist(self, x, bins=10, range=None, normed=False, weights=None,
        hist_kwargs = dict(range=bin_range)

        n = []
-        mlast = bottom
+        mlast = None
        for i in xrange(nx):
            # this will automatically overwrite bins,
            # so that each histogram uses the same bins
            m, bins = np.histogram(x[i], bins, weights=w[i], **hist_kwargs)
            m = m.astype(float) # causes problems later if it's an int
-            if mlast is None:
-                mlast = np.zeros(len(bins)-1, m.dtype)
            if normed and not stacked:
                db = np.diff(bins)
                m = (m.astype(float) / db) / m.sum()
            if stacked:
+                if mlast is None:
+                    mlast = np.zeros(len(bins)-1, m.dtype)
                m += mlast
                mlast[:] = m
            n.append(m)
@@ -8421,6 +8421,12 @@ def hist(self, x, bins=10, range=None, normed=False, weights=None,
            x[0:2*len(bins)-1:2], x[1:2*len(bins)-1:2] = bins, bins[:-1]
            x[2*len(bins)-1:] = x[1:2*len(bins)-1][::-1]

+            if bottom is None:
+                bottom = np.zeros(len(bins)-1, np.float)
+
+            y[1:2*len(bins)-1:2], y[2:2*len(bins):2] = bottom, bottom
+            y[2*len(bins)-1:] = y[1:2*len(bins)-1][::-1]
+
            if log:
                if orientation == 'horizontal':
                    self.set_xscale('log', nonposx='clip')
@@ -8456,12 +8462,13 @@ def hist(self, x, bins=10, range=None, normed=False, weights=None,

            xvals, yvals = [], []
            for m in n:
-                # starting point for drawing polygon
-                y[0] = y[1]
-                # top of the previous polygon becomes the bottom
-                y[2*len(bins)-1:] = y[1:2*len(bins)-1][::-1]
+                if stacked:
+                    # starting point for drawing polygon
+                    y[0] = y[1]
+                    # top of the previous polygon becomes the bottom
+                    y[2*len(bins)-1:] = y[1:2*len(bins)-1][::-1]
                # set the top of this polygon
-                y[1:2*len(bins)-1:2], y[2:2*len(bins)-1:2] = m, m
+                y[1:2*len(bins)-1:2], y[2:2*len(bins):2] = m + bottom, m + bottom
                if log:
                    y[y < minimum] = minimum
                if orientation == 'horizontal':

diff --git a/lib/matplotlib/tests/baseline_images/test_axes/hist_step_bottom.png b/lib/matplotlib/tests/baseline_images/test_axes/hist_step_bottom.png
diff --git a/lib/matplotlib/tests/test_axes.py b/lib/matplotlib/tests/test_axes.py
@@ -1127,6 +1127,15 @@ def test_hist_stacked_normed():
    ax.hist((d1, d2), stacked=True, normed=True)


+@image_comparison(baseline_images=['hist_step_bottom'], extensions=['png'], remove_text=True)
+def test_hist_step_bottom():
+    # make some data
+    d1 = np.linspace(1, 3, 20)
+    fig = plt.figure()
+    ax = fig.add_subplot(111)
+    ax.hist(d1, bottom=np.arange(10), histtype="stepfilled")
+
+
 @image_comparison(baseline_images=['hist_stacked_bar'])
 def test_hist_stacked_bar():
    # make some data