1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
|
#!/usr/bin/env python
# -*- coding: utf-8 -*-
import numpy as np
import matplotlib.pyplot as plt
import pywt
import pywt.data
ecg = pywt.data.ecg()
data1 = np.concatenate((np.arange(1, 400),
np.arange(398, 600),
np.arange(601, 1024)))
x = np.linspace(0.082, 2.128, num=1024)[::-1]
data2 = np.sin(40 * np.log(x)) * np.sign((np.log(x)))
mode = pywt.Modes.sp1DWT = 1
def plot_coeffs(data, w, title, use_dwt=True):
"""Show dwt or swt coefficients for given data and wavelet."""
w = pywt.Wavelet(w)
a = data
ca = []
cd = []
if use_dwt:
for i in range(5):
(a, d) = pywt.dwt(a, w, mode)
ca.append(a)
cd.append(d)
else:
coeffs = pywt.swt(data, w, 5) # [(cA5, cD5), ..., (cA1, cD1)]
for a, d in reversed(coeffs):
ca.append(a)
cd.append(d)
fig = plt.figure()
ax_main = fig.add_subplot(len(ca) + 1, 1, 1)
ax_main.set_title(title)
ax_main.plot(data)
ax_main.set_xlim(0, len(data) - 1)
for i, x in enumerate(ca):
ax = fig.add_subplot(len(ca) + 1, 2, 3 + i * 2)
ax.plot(x, 'r')
ax.set_ylabel("A%d" % (i + 1))
if use_dwt:
ax.set_xlim(0, len(x) - 1)
else:
ax.set_xlim(w.dec_len * i, len(x) - 1 - w.dec_len * i)
for i, x in enumerate(cd):
ax = fig.add_subplot(len(cd) + 1, 2, 4 + i * 2)
ax.plot(x, 'g')
ax.set_ylabel("D%d" % (i + 1))
# Scale axes
ax.set_xlim(0, len(x) - 1)
if use_dwt:
ax.set_ylim(min(0, 1.4 * min(x)), max(0, 1.4 * max(x)))
else:
vals = x[w.dec_len * (1 + i):len(x) - w.dec_len * (1 + i)]
ax.set_ylim(min(0, 2 * min(vals)), max(0, 2 * max(vals)))
# Show DWT coefficients
use_dwt = True
plot_coeffs(data1, 'db1',
"DWT: Signal irregularity shown in D1 - Haar wavelet",
use_dwt)
plot_coeffs(data2, 'sym5', "DWT: Frequency and phase change - Symmlets5",
use_dwt)
plot_coeffs(ecg, 'sym5', "DWT: Ecg sample - Symmlets5", use_dwt)
# Show DWT coefficients
use_dwt = False
plot_coeffs(data1, 'db1', "SWT: Signal irregularity detection - Haar wavelet",
use_dwt)
plot_coeffs(data2, 'sym5', "SWT: Frequency and phase change - Symmlets5",
use_dwt)
plot_coeffs(ecg, 'sym5', "SWT: Ecg sample - simple QRS detection - Symmlets5",
use_dwt)
plt.show()
|
