.. _pylab_examples-cohere_demo:

pylab_examples example code: cohere_demo.py
===========================================



.. plot:: /home/mandrake/rpm/BUILD/matplotlib-1.1.1/doc/mpl_examples/pylab_examples/cohere_demo.py

::

    #!/usr/bin/env python
    """
    Compute the coherence of two signals
    """
    import numpy as np
    import matplotlib.pyplot as plt
    
    # make a little extra space between the subplots
    plt.subplots_adjust(wspace=0.5)
    
    dt = 0.01
    t = np.arange(0, 30, dt)
    nse1 = np.random.randn(len(t))                 # white noise 1
    nse2 = np.random.randn(len(t))                 # white noise 2
    r = np.exp(-t/0.05)
    
    cnse1 = np.convolve(nse1, r, mode='same')*dt   # colored noise 1
    cnse2 = np.convolve(nse2, r, mode='same')*dt   # colored noise 2
    
    # two signals with a coherent part and a random part
    s1 = 0.01*np.sin(2*np.pi*10*t) + cnse1
    s2 = 0.01*np.sin(2*np.pi*10*t) + cnse2
    
    plt.subplot(211)
    plt.plot(t, s1, 'b-', t, s2, 'g-')
    plt.xlim(0,5)
    plt.xlabel('time')
    plt.ylabel('s1 and s2')
    plt.grid(True)
    
    plt.subplot(212)
    cxy, f = plt.cohere(s1, s2, 256, 1./dt)
    plt.ylabel('coherence')
    plt.show()
    
    
    

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