Add stacked kwarg to hist and implement stacked hists for step histtype

doc/users/whats_new.rst

@@ -127,6 +127,17 @@ local intensity of the vector field.
 
 .. plot:: mpl_examples/pylab_examples/streamplot_demo.py
 
+
+New hist functionality
+----------------------
+
+Nic Eggert added a new `stacked` kwarg to :meth:`~matplotlib.pyplot.hist` that
+allows creation of stacked histograms using any of the histogram types.
+Previously, this functionality was only available by using the `barstacked`
+histogram type. Now, when `stacked=True` is passed to the function, any of the
+histogram types can be stacked. The `barstacked` histogram type retains its
+previous functionality for backwards compatibility.
+
 Updated shipped dependencies
 ----------------------------
 

examples/pylab_examples/histogram_demo_extended.py

@@ -82,7 +82,19 @@
 #
 P.figure()
 
-n, bins, patches = P.hist(x, 10, normed=1, histtype='barstacked')
+n, bins, patches = P.hist(x, 10, normed=1, histtype='bar', stacked=True)
+
+P.show()
+
+#
+# we can also stack using the step histtype
+#
+
+P.figure()
+
+n, bins, patches = P.hist(x, 10, histtype='step', stacked=True, fill=True)
+
+P.show()
 
 #
 # finally: make a multiple-histogram of data-sets with different length

lib/matplotlib/axes.py

@@ -7728,7 +7728,7 @@ def get_shared_y_axes(self):
     def hist(self, x, bins=10, range=None, normed=False, weights=None,
              cumulative=False, bottom=None, histtype='bar', align='mid',
              orientation='vertical', rwidth=None, log=False,
-             color=None, label=None,
+             color=None, label=None, stacked=False,
              **kwargs):
         """
         Plot a histogram.
@@ -7738,7 +7738,7 @@ def hist(self, x, bins=10, range=None, normed=False, weights=None,
           hist(x, bins=10, range=None, normed=False, weights=None,
                  cumulative=False, bottom=None, histtype='bar', align='mid',
                  orientation='vertical', rwidth=None, log=False,
-                 color=None, label=None,
+                 color=None, label=None, stacked=False,
                  **kwargs)
 
         Compute and draw the histogram of *x*. The return value is a
@@ -7862,6 +7862,11 @@ def hist(self, x, bins=10, range=None, normed=False, weights=None,
                 ax.hist(12+3*np.random.randn(1000), label='women', alpha=0.5)
                 ax.legend()
 
+          *stacked*:
+            If *True*, multiple data are stacked on top of each other
+            If *False* multiple data are aranged side by side if
+            histtype is 'bar' or on top of each other if histtype is 'step'
+
             .
 
         kwargs are used to update the properties of the
@@ -7901,6 +7906,9 @@ def hist(self, x, bins=10, range=None, normed=False, weights=None,
                 'hist now uses the rwidth to give relative width '
                 'and not absolute width')
 
+        if histtype == 'barstacked' and not stacked:
+            stacked=True
+
         # Massage 'x' for processing.
         # NOTE: Be sure any changes here is also done below to 'weights'
         if isinstance(x, np.ndarray) or not iterable(x[0]):
@@ -7986,13 +7994,21 @@ def hist(self, x, bins=10, range=None, normed=False, weights=None,
             hist_kwargs['new'] = True
 
         n = []
-        for i in xrange(nx):
+        mlast = bottom
+        # reversed order is necessary so when stacking histogram, first dataset is on top
+        # if histogram isn't stacked, this doesn't make any difference
+        for i in reversed(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)
+            if mlast is None:
+                mlast = np.zeros(len(bins)-1, np.int)
             if normed:
                 db = np.diff(bins)
                 m = (m.astype(float) / db) / m.sum()
+            if stacked:
+                m += mlast
+                mlast[:] = m
             n.append(m)
 
         if cumulative:
@@ -8005,6 +8021,8 @@ def hist(self, x, bins=10, range=None, normed=False, weights=None,
             else:
                 n = [m[slc].cumsum()[slc] for m in n]
 
+        n.reverse() # put them back in the right order
+
         patches = []
 
         if histtype.startswith('bar'):
@@ -8017,7 +8035,7 @@ def hist(self, x, bins=10, range=None, normed=False, weights=None,
             else:
                 dr = 1.0
 
-            if histtype=='bar':
+            if histtype=='bar' and not stacked:
                 width = dr*totwidth/nx
                 dw = width
 
@@ -8026,10 +8044,9 @@ def hist(self, x, bins=10, range=None, normed=False, weights=None,
                 else:
                     boffset = 0.0
                 stacked = False
-            elif histtype=='barstacked':
+            elif histtype=='barstacked' or stacked:
                 width = dr*totwidth
                 boffset, dw = 0.0, 0.0
-                stacked = True
 
             if align == 'mid' or align == 'edge':
                 boffset += 0.5*totwidth
@@ -8042,14 +8059,10 @@ def hist(self, x, bins=10, range=None, normed=False, weights=None,
                 _barfunc = self.bar
 
             for m, c in zip(n, color):
-                patch = _barfunc(bins[:-1]+boffset, m, width, bottom,
+                patch = _barfunc(bins[:-1]+boffset, m, width,
                                   align='center', log=log,
                                   color=c)
                 patches.append(patch)
-                if stacked:
-                    if bottom is None:
-                        bottom = 0.0
-                    bottom += m
                 boffset += dw
 
         elif histtype.startswith('step'):
@@ -8072,6 +8085,8 @@ def hist(self, x, bins=10, range=None, normed=False, weights=None,
                 else:  # orientation == 'vertical'
                     self.set_yscale('log')
 
+            # If fill kwarg is set, it will be passed to the patch collection,
+            # overriding this
             fill = (histtype == 'stepfilled')
 
             for m, c in zip(n, color):

lib/matplotlib/pyplot.py

@@ -2642,7 +2642,8 @@ def hexbin(x, y, C=None, gridsize=100, bins=None, xscale='linear',
 @_autogen_docstring(Axes.hist)
 def hist(x, bins=10, range=None, normed=False, weights=None, cumulative=False,
          bottom=None, histtype='bar', align='mid', orientation='vertical',
-         rwidth=None, log=False, color=None, label=None, hold=None, **kwargs):
+         rwidth=None, log=False, color=None, label=None, stacked=False,
+         hold=None, **kwargs):
     ax = gca()
     # allow callers to override the hold state by passing hold=True|False
     washold = ax.ishold()