.. _animation-histogram:

animation example code: histogram.py
====================================

[`source code <histogram.py>`_]

::

    """
    This example shows how to use a path patch to draw a bunch of
    rectangles for an animated histogram
    """
    import numpy as np
    
    import matplotlib.pyplot as plt
    import matplotlib.patches as patches
    import matplotlib.path as path
    import matplotlib.animation as animation
    
    fig = plt.figure()
    ax = fig.add_subplot(111)
    
    # histogram our data with numpy
    data = np.random.randn(1000)
    n, bins = np.histogram(data, 100)
    
    # get the corners of the rectangles for the histogram
    left = np.array(bins[:-1])
    right = np.array(bins[1:])
    bottom = np.zeros(len(left))
    top = bottom + n
    nrects = len(left)
    
    # here comes the tricky part -- we have to set up the vertex and path
    # codes arrays using moveto, lineto and closepoly
    
    # for each rect: 1 for the MOVETO, 3 for the LINETO, 1 for the
    # CLOSEPOLY; the vert for the closepoly is ignored but we still need
    # it to keep the codes aligned with the vertices
    nverts = nrects*(1+3+1)
    verts = np.zeros((nverts, 2))
    codes = np.ones(nverts, int) * path.Path.LINETO
    codes[0::5] = path.Path.MOVETO
    codes[4::5] = path.Path.CLOSEPOLY
    verts[0::5,0] = left
    verts[0::5,1] = bottom
    verts[1::5,0] = left
    verts[1::5,1] = top
    verts[2::5,0] = right
    verts[2::5,1] = top
    verts[3::5,0] = right
    verts[3::5,1] = bottom
    
    barpath = path.Path(verts, codes)
    patch = patches.PathPatch(barpath, facecolor='green', edgecolor='yellow', alpha=0.5)
    ax.add_patch(patch)
    
    ax.set_xlim(left[0], right[-1])
    ax.set_ylim(bottom.min(), top.max())
    
    def animate(i):
        # simulate new data coming in
        data = np.random.randn(1000)
        n, bins = np.histogram(data, 100)
        top = bottom + n
        verts[1::5,1] = top
        verts[2::5,1] = top
    
    ani = animation.FuncAnimation(fig, animate, 100, repeat=False)
    plt.show()
    

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