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#!/usr/bin/env python
# -*- coding: utf-8 -*-
import numpy as np
import matplotlib.pyplot as plt
import pywt
x = np.linspace(0, 1, num=512)
data = np.sin(250 * np.pi * x**2)
wavelet = 'db2'
level = 4
order = "freq" # other option is "normal"
interpolation = 'nearest'
cmap = plt.cm.cool
# Construct wavelet packet
wp = pywt.WaveletPacket(data, wavelet, 'symmetric', maxlevel=level)
nodes = wp.get_level(level, order=order)
labels = [n.path for n in nodes]
values = np.array([n.data for n in nodes], 'd')
values = abs(values)
# Show signal and wavelet packet coefficients
fig = plt.figure()
fig.subplots_adjust(hspace=0.2, bottom=.03, left=.07, right=.97, top=.92)
ax = fig.add_subplot(2, 1, 1)
ax.set_title("linchirp signal")
ax.plot(x, data, 'b')
ax.set_xlim(0, x[-1])
ax = fig.add_subplot(2, 1, 2)
ax.set_title("Wavelet packet coefficients at level %d" % level)
ax.imshow(values, interpolation=interpolation, cmap=cmap, aspect="auto",
origin="lower", extent=[0, 1, 0, len(values)])
ax.set_yticks(np.arange(0.5, len(labels) + 0.5), labels)
# Show spectrogram and wavelet packet coefficients
fig2 = plt.figure()
ax2 = fig2.add_subplot(211)
ax2.specgram(data, NFFT=64, noverlap=32, Fs=2, cmap=cmap,
interpolation='bilinear')
ax2.set_title("Spectrogram of signal")
ax3 = fig2.add_subplot(212)
ax3.imshow(values, origin='upper', extent=[-1, 1, -1, 1],
interpolation='nearest')
ax3.set_title("Wavelet packet coefficients")
plt.show()
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