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pylab_examples example code: csd_demo.pyΒΆ

(Source code, png, hires.png, pdf)

#!/usr/bin/env python
Compute the cross spectral density of two signals
import numpy as np
import matplotlib.pyplot as plt

# make a little extra space between the subplots

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.plot(t, s1, 'b-', t, s2, 'g-')
plt.xlim(0, 5)
plt.ylabel('s1 and s2')

cxy, f = plt.csd(s1, s2, 256, 1./dt)
plt.ylabel('CSD (db)')

Keywords: python, matplotlib, pylab, example, codex (see Search examples)