.. _api-hinton_demo:

api example code: hinton_demo.py
================================



.. plot:: /home/mdboom/Work/builds/matplotlib/doc/mpl_examples/api/hinton_demo.py

::

    #Initial idea from David Warde-Farley on the SciPy Cookbook
    import numpy as np
    import matplotlib.pyplot as plt
    from matplotlib.patches import Rectangle
    from matplotlib.ticker import NullLocator
    #from matplotlib.collections import RegularPolyCollection
    #from matplotlib.colors import BoundaryNorm, ListedColormap
    
    def hinton(W, maxWeight=None, ax=None):
        """
        Draws a Hinton diagram for visualizing a weight matrix.
        """
        if not ax:
            fig = plt.figure()
            ax = fig.add_subplot(1, 1, 1)
    
        if not maxWeight:
            maxWeight = 2**np.ceil(np.log(np.abs(W).max())/np.log(2))
    
        ax.patch.set_facecolor('gray')
        ax.set_aspect('equal', 'box')
        ax.xaxis.set_major_locator(NullLocator())
        ax.yaxis.set_major_locator(NullLocator())
    
        for (x,y),w in np.ndenumerate(W):
            if w > 0: color = 'white'
            else:     color = 'black'
            size = np.sqrt(np.abs(w))
            rect = Rectangle([x - size / 2, y - size / 2], size, size,
                facecolor=color, edgecolor=color)
            ax.add_patch(rect)
        ax.autoscale_view()
    
        # Reverse the yaxis limits
        ax.set_ylim(*ax.get_ylim()[::-1])
    
    ## Potential way using polygon collections that just has an issue with
    ## easily getting the squares scaled by the data.
    
    #    height,width = W.shape
    #    x = np.arange(width)
    #    y = np.arange(height)
    #    X,Y = np.meshgrid(x, y)
    #    xy = np.array([X.flatten(),Y.flatten()]).T
    #    scaled_data = W.flatten() / maxWeight
    #    cmap = ListedColormap(['black', 'white'])
    #    norm = BoundaryNorm([-1., 0., 1.], cmap.N)
    
    #    rect_col = RegularPolyCollection(4, rotation=np.pi/4,
    #        sizes=np.abs(scaled_data) * 72 / ax.figure.get_dpi(), offsets=xy,
    #        transOffset=ax.transData, norm=norm, cmap=cmap, edgecolor='none')
    #    ax.add_collection(rect_col)
    #    rect_col.set_array(scaled_data)
    #    ax.autoscale_view()
    
    if __name__ == '__main__':
        hinton(np.random.rand(20, 20) - 0.5)
        plt.title('Hinton Example')
        plt.show()
    
    

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