Merge pull request matplotlib#1684 from dmcdougall/fix_loghist

Fix hist for log=True and histtype='step'

Author: dmcdougall

lib/matplotlib/axes.py

@@ -8184,19 +8184,33 @@ def hist(self, x, bins=10, range=None, normed=False, weights=None,
 
             x[0::2], x[1::2] = bins, bins
 
-            minimum = np.min(n)
-
-            if align == 'left' or align == 'center':
-                x -= 0.5*(bins[1]-bins[0])
-            elif align == 'right':
-                x += 0.5*(bins[1]-bins[0])
-
             if log:
-                y[0],y[-1] = minimum, minimum
                 if orientation == 'horizontal':
                     self.set_xscale('log')
+                    logbase = self.xaxis._scale.base
                 else:  # orientation == 'vertical'
                     self.set_yscale('log')
+                    logbase = self.yaxis._scale.base
+
+                # Setting a minimum of 0 results in problems for log plots
+                if normed:
+                    # For normed data, set to log base * minimum data value
+                    # (gives 1 full tick-label unit for the lowest filled bin)
+                    ndata = np.array(n)
+                    minimum = (np.min(ndata[ndata>0])) / logbase
+                else:
+                    # For non-normed data, set the min to log base, again so that
+                    # there is 1 full tick-label unit for the lowest bin
+                    minimum = 1.0 / logbase
+
+                y[0], y[-1] = minimum, minimum
+            else:
+                minimum = np.min(bins)
+
+            if align == 'left' or align == 'center':
+                x -= 0.5*(bins[1]-bins[0])
+            elif align == 'right':
+                x += 0.5*(bins[1]-bins[0])
 
             # If fill kwarg is set, it will be passed to the patch collection,
             # overriding this