最近正在學(xué)習(xí)音頻方面的項(xiàng)目，涉及到了小波變換的內(nèi)容。pywavelets是其中一個(gè)比較常見(jiàn)的小波模塊春感。復(fù)現(xiàn)了下其他博客如下：小波變換-python pywavelets
np.piecewise是根據(jù)條件篩選，然后執(zhí)行例如lambda/函數(shù)等操作。參考鏈接np.piecewise
#!/usr/bin/env python
# encoding: utf-8
import numpy as np
import matplotlib.pyplot as plt
import pywt
sampling_rate = 1024#采樣頻率
t = np.arange(0,1.0,1.0/sampling_rate)
f1 = 100#頻率
f2 = 200
f3 = 300
data = np.piecewise(t,[t<1,t<0.8,t<0.3],
[lambda t : np.sin(2*np.pi *f1*t),
lambda t : np.sin(2 * np.pi * f2 * t),
lambda t : np.sin(2 * np.pi * f3 * t)])
wavename = "cgau8"
totalscal = 256
fc = pywt.central_frequency(wavename)#中心頻率
cparam = 2 * fc * totalscal
scales = cparam/np.arange(totalscal,1,-1)
[cwtmatr, frequencies] = pywt.cwt(data,scales,wavename,1.0/sampling_rate)#連續(xù)小波變換
plt.figure(figsize=(8, 4))
plt.subplot(211)
plt.plot(t, data)
plt.xlabel(u"time(s)")
plt.title(u"300Hz 200Hz 100Hz Time spectrum")
plt.subplot(212)
plt.contourf(t, frequencies, abs(cwtmatr))
plt.ylabel(u"freq(Hz)")
plt.xlabel(u"time(s)")
plt.subplots_adjust(hspace=0.4)
plt.show()
效果圖
[Python ]小波變化庫(kù)——Pywalvets 學(xué)習(xí)筆記
有些地方?jīng)]弄懂村象，仍不斷學(xué)習(xí)中。
