matplotlib/examples/cohere_demo.py at transforms · staticor/matplotlib · GitHub

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#!/usr/bin/env python

"""

Compute the coherence of two signals

"""

import numpy as n

from pylab import figure, show

dt = 0.01

t = n.arange(0, 30, dt)

Nt = len(t)

nse1 = n.random.randn(Nt) # white noise 1

nse2 = n.random.randn(Nt) # white noise 2

r = n.exp(-t/0.05)

cnse1 = n.convolve(nse1, r)*dt # colored noise 1

cnse1 = cnse1[:Nt]

cnse2 = n.convolve(nse2, r)*dt # colored noise 2

cnse2 = cnse2[:Nt]

# two signals with a coherent part and a random part

s1 = 0.01*n.sin(2*n.pi*10*t) + cnse1

s2 = 0.01*n.sin(2*n.pi*10*t) + cnse2

fig = figure()

ax = fig.add_subplot(211)

ax.plot(t, s1, 'b-', t, s2, 'g-')

ax.set_xlim(0,5)

ax.set_xlabel('time')

ax.set_ylabel('s1 and s2')

ax = fig.add_subplot(212)

cxy, f = ax.cohere(s1, s2, 256, 1./dt)

show()