.. _images_contours_and_fields-streamplot_demo_start_points:

images_contours_and_fields example code: streamplot_demo_start_points.py
========================================================================



.. plot:: /home/tcaswell/source/p/matplotlib/doc/mpl_examples/images_contours_and_fields/streamplot_demo_start_points.py

::

    """
    Demo of the `streamplot` function.
    
    A streamplot, or streamline plot, is used to display 2D vector fields. This
    example shows a few features of the stream plot function:
    
        * Varying the color along a streamline.
        * Varying the density of streamlines.
        * Varying the line width along a stream line.
    """
    import numpy as np
    import matplotlib.pyplot as plt
    
    X, Y = (np.linspace(-3, 3, 100),
            np.linspace(-3, 3, 100))
    
    U, V = np.mgrid[-3:3:100j, 0:0:100j]
    
    seed_points = np.array([[-2, 0, 1], [-2, 0, 1]])
    
    fig0, ax0 = plt.subplots()
    strm = ax0.streamplot(X, Y, U, V, color=U, linewidth=2,
                          cmap=plt.cm.autumn, start_points=seed_points.T)
    fig0.colorbar(strm.lines)
    
    ax0.plot(seed_points[0], seed_points[1], 'bo')
    
    ax0.axis((-3, 3, -3, 3))
    
    plt.show()
    

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