.. _pylab_examples-scatter_demo2:

pylab_examples example code: scatter_demo2.py
=============================================



.. plot:: /home/tcaswell/source/p/matplotlib/doc/mpl_examples/pylab_examples/scatter_demo2.py

::

    """
    Demo of scatter plot with varying marker colors and sizes.
    """
    import numpy as np
    import matplotlib.pyplot as plt
    import matplotlib.cbook as cbook
    
    # Load a numpy record array from yahoo csv data with fields date,
    # open, close, volume, adj_close from the mpl-data/example directory.
    # The record array stores python datetime.date as an object array in
    # the date column
    datafile = cbook.get_sample_data('goog.npy')
    try:
        # Python3 cannot load python2 .npy files with datetime(object) arrays
        # unless the encoding is set to bytes. However this option was
        # not added until numpy 1.10 so this example will only work with
        # python 2 or with numpy 1.10 and later
        price_data = np.load(datafile, encoding='bytes').view(np.recarray)
    except TypeError:
        price_data = np.load(datafile).view(np.recarray)
    price_data = price_data[-250:]  # get the most recent 250 trading days
    
    delta1 = np.diff(price_data.adj_close)/price_data.adj_close[:-1]
    
    # Marker size in units of points^2
    volume = (15 * price_data.volume[:-2] / price_data.volume[0])**2
    close = 0.003 * price_data.close[:-2] / 0.003 * price_data.open[:-2]
    
    fig, ax = plt.subplots()
    ax.scatter(delta1[:-1], delta1[1:], c=close, s=volume, alpha=0.5)
    
    ax.set_xlabel(r'$\Delta_i$', fontsize=15)
    ax.set_ylabel(r'$\Delta_{i+1}$', fontsize=15)
    ax.set_title('Volume and percent change')
    
    ax.grid(True)
    fig.tight_layout()
    
    plt.show()
    

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