matplotlib-users

[Matplotlib-users] Histogram without probability

[nbv4 <cp3...@oh...>]

The histogram example in the matpolotlib gallery is just what I want, except
instead of "probility" shown on the Y-axis, I want the number of items that
fall into each bin to be plotted. How do I do this? Here is my code:

        import numpy as np
        import matplotlib
        matplotlib.use('Agg')
        import matplotlib.pyplot as plt

        fig = plt.figure()
        ax = fig.add_subplot(111)

        x = self.data ## a list, such as [12.43, 34.24, 35.56, 465.3547, ]
        ax.hist(x, 60, normed=1, facecolor='green', alpha=0.75)

        ax.set_xlabel('Totals')
        ax.set_ylabel('Number of Users'))
        ax.set_xlim(0, 2000)
        ax.set_ylim(0, 0.003)
        ax.grid(True)
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Re: [Matplotlib-users] Histogram without probability

[Ryan M. <rm...@gm...>]

On Mon, Dec 14, 2009 at 7:22 PM, nbv4 <cp3...@oh...> wrote:
>
> The histogram example in the matpolotlib gallery is just what I want, except
> instead of "probility" shown on the Y-axis, I want the number of items that
> fall into each bin to be plotted. How do I do this? Here is my code:
>
>        import numpy as np
>        import matplotlib
>        matplotlib.use('Agg')
>        import matplotlib.pyplot as plt
>
>        fig = plt.figure()
>        ax = fig.add_subplot(111)
>
>        x = self.data ## a list, such as [12.43, 34.24, 35.56, 465.3547, ]
>        ax.hist(x, 60, normed=1, facecolor='green', alpha=0.75)

>From the docstring for ax.hist:

      *normed*:
        If *True*, the first element of the return tuple will
        be the counts normalized to form a probability density, i.e.,
        ``n/(len(x)*dbin)``.  In a probability density, the integral of
        the histogram should be 1; you can verify that with a
        trapezoidal integration of the probability density function::

          pdf, bins, patches = ax.hist(...)
          print np.sum(pdf * np.diff(bins))

So instead, pass normed=False (instead of normed=1) to the call to ax.hist.

Ryan

-- 
Ryan May
Graduate Research Assistant
School of Meteorology
University of Oklahoma

Re: [Matplotlib-users] Histogram without probability

[Eric F. <ef...@ha...>]

nbv4 wrote:
> The histogram example in the matpolotlib gallery is just what I want, except
> instead of "probility" shown on the Y-axis, I want the number of items that
> fall into each bin to be plotted. How do I do this? Here is my code:
> 
>         import numpy as np
>         import matplotlib
>         matplotlib.use('Agg')
>         import matplotlib.pyplot as plt
> 
>         fig = plt.figure()
>         ax = fig.add_subplot(111)
> 
>         x = self.data ## a list, such as [12.43, 34.24, 35.56, 465.3547, ]
>         ax.hist(x, 60, normed=1, facecolor='green', alpha=0.75)

Leave out the "normed" kwarg, or set it to False (the default).

http://matplotlib.sourceforge.net/api/pyplot_api.html#matplotlib.pyplot.hist

> 
>         ax.set_xlabel('Totals')
>         ax.set_ylabel('Number of Users'))
>         ax.set_xlim(0, 2000)
>         ax.set_ylim(0, 0.003)
>         ax.grid(True)