.. _specialty_plots-hinton_demo:

specialty_plots example code: hinton_demo.py
============================================



.. plot:: /builddir/build/BUILD/matplotlib-1.3.1/doc/mpl_examples/specialty_plots/hinton_demo.py

::

    """
    Demo of a function to create Hinton diagrams.
    
    Hinton diagrams are useful for visualizing the values of a 2D array (e.g.
    a weight matrix): Positive and negative values are represented by white and
    black squares, respectively, and the size of each square represents the
    magnitude of each value.
    
    Initial idea from David Warde-Farley on the SciPy Cookbook
    """
    import numpy as np
    import matplotlib.pyplot as plt
    
    
    def hinton(matrix, max_weight=None, ax=None):
        """Draw Hinton diagram for visualizing a weight matrix."""
        ax = ax if ax is not None else plt.gca()
    
        if not max_weight:
            max_weight = 2**np.ceil(np.log(np.abs(matrix).max())/np.log(2))
    
        ax.patch.set_facecolor('gray')
        ax.set_aspect('equal', 'box')
        ax.xaxis.set_major_locator(plt.NullLocator())
        ax.yaxis.set_major_locator(plt.NullLocator())
    
        for (x,y),w in np.ndenumerate(matrix):
            color = 'white' if w > 0 else 'black'
            size = np.sqrt(np.abs(w))
            rect = plt.Rectangle([x - size / 2, y - size / 2], size, size,
                                 facecolor=color, edgecolor=color)
            ax.add_patch(rect)
    
        ax.autoscale_view()
        ax.invert_yaxis()
    
    
    if __name__ == '__main__':
        hinton(np.random.rand(20, 20) - 0.5)
        plt.show()
    
    

Keywords: python, matplotlib, pylab, example, codex (see :ref:`how-to-search-examples`)