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DOC: Switch to OO code style & ensure fixed y-range in psd_demo3 #6841

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Jul 28, 2016
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DOC: Switch to OO code style & ensure fixed y-range in psd_demo3 #6841

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382b319
Switch to OO code style & ensure y-range
afvincent Jul 26, 2016
be8e253
Use a RandomState instance with a fixed seed
afvincent Jul 26, 2016
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43 changes: 25 additions & 18 deletions examples/pylab_examples/psd_demo3.py
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Original file line number Diff line number Diff line change
@@ -1,36 +1,43 @@
# This is a ported version of a MATLAB example from the signal processing
# toolbox that showed some difference at one time between Matplotlib's and
# MATLAB's scaling of the PSD.
"""This is a ported version of a MATLAB example from the signal
processing toolbox that showed some difference at one time between
Matplotlib's and MATLAB's scaling of the PSD.

"""

import numpy as np
import matplotlib.pyplot as plt
import matplotlib.mlab as mlab

prng = np.random.RandomState(123456) # to ensure reproducibility

fs = 1000
t = np.linspace(0, 0.3, 301)
A = np.array([2, 8]).reshape(-1, 1)
f = np.array([150, 140]).reshape(-1, 1)
xn = (A * np.sin(2 * np.pi * f * t)).sum(axis=0) + 5 * np.random.randn(*t.shape)
xn = (A * np.sin(2 * np.pi * f * t)).sum(axis=0) + 5 * prng.randn(*t.shape)

fig, (ax0, ax1) = plt.subplots(ncols=2)

fig.subplots_adjust(hspace=0.45, wspace=0.3)
yticks = np.arange(-50, 30, 10)
yrange = (yticks[0], yticks[-1])
xticks = np.arange(0, 550, 100)
plt.subplots_adjust(hspace=0.45, wspace=0.3)
plt.subplot(1, 2, 1)

plt.psd(xn, NFFT=301, Fs=fs, window=mlab.window_none, pad_to=1024,
ax0.psd(xn, NFFT=301, Fs=fs, window=mlab.window_none, pad_to=1024,
scale_by_freq=True)
plt.title('Periodogram')
plt.yticks(yticks)
plt.xticks(xticks)
plt.grid(True)
ax0.set_title('Periodogram')
ax0.set_yticks(yticks)
ax0.set_xticks(xticks)
ax0.grid(True)
ax0.set_ylim(yrange)

plt.subplot(1, 2, 2)
plt.psd(xn, NFFT=150, Fs=fs, window=mlab.window_none, noverlap=75, pad_to=512,
ax1.psd(xn, NFFT=150, Fs=fs, window=mlab.window_none, pad_to=512, noverlap=75,
scale_by_freq=True)
plt.title('Welch')
plt.xticks(xticks)
plt.yticks(yticks)
plt.ylabel('')
plt.grid(True)
ax1.set_title('Welch')
ax1.set_xticks(xticks)
ax1.set_yticks(yticks)
ax1.set_ylabel('') # overwrite the y-label added by `psd`
ax1.grid(True)
ax1.set_ylim(yrange)

plt.show()