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# 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) / max_weight)
            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__':
        # Fixing random state for reproducibility
        np.random.seed(19680801)

        hinton(np.random.rand(20, 20) - 0.5)
        plt.show()

Total running time of the script: ( 0 minutes 0.283 seconds)

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