matplotlib/matplotlib — pull request #1833 by neggert (2013-03-17 20:08:04+00:00)
Title: Change hist behavior when normed and stacked to something more sensible

This addresses #1745. Previously, when passed `stacked=True, normed=True`, `hist` would normalize the histogram for each dataset, then stack them, which is, IMO, not what most users would want. With this PR, `hist` will first stack the histograms, then normalize them such that the integral of the stacked histograms equals 1.