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# Generate polygons to fill under 3D line graph

Demonstrate how to create polygons which fill the space under a line graph. In this example polygons are semi-transparent, creating a sort of ‘jagged stained glass’ effect.

    from mpl_toolkits.mplot3d import Axes3D
    from matplotlib.collections import PolyCollection
    import matplotlib.pyplot as plt
    from matplotlib import colors as mcolors
    import numpy as np

    # Fixing random state for reproducibility
    np.random.seed(19680801)

    def cc(arg):
        '''
        Shorthand to convert 'named' colors to rgba format at 60% opacity.
        '''
        return mcolors.to_rgba(arg, alpha=0.6)

    def polygon_under_graph(xlist, ylist):
        '''
        Construct the vertex list which defines the polygon filling the space under
        the (xlist, ylist) line graph.  Assumes the xs are in ascending order.
        '''
        return [(xlist[0], 0.)] + list(zip(xlist, ylist)) + [(xlist[-1], 0.)]

    fig = plt.figure()
    ax = fig.gca(projection='3d')

    # Make verts a list, verts[i] will be a list of (x,y) pairs defining polygon i
    verts = []

    # Set up the x sequence
    xs = np.linspace(0., 10., 26)

    # The ith polygon will appear on the plane y = zs[i]
    zs = range(4)

    for i in zs:
        ys = np.random.rand(len(xs))
        verts.append(polygon_under_graph(xs, ys))

    poly = PolyCollection(verts, facecolors=[cc('r'), cc('g'), cc('b'), cc('y')])
    ax.add_collection3d(poly, zs=zs, zdir='y')

    ax.set_xlabel('X')
    ax.set_ylabel('Y')
    ax.set_zlabel('Z')
    ax.set_xlim(0, 10)
    ax.set_ylim(-1, 4)
    ax.set_zlim(0, 1)

    plt.show()

Total running time of the script: ( 0 minutes 0.021 seconds)

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