波动信号的包络线MATLAB程序生成

truleeee

1. <font color="#000000">此程序源自MATLAB CENTRAL。
   
2. % Find upper and lower envelopes of a given signal
   
3. % The idea is from Envelope1.1 by Lei Wang, but here it works well when the signal contains
   
4. % successive equal samples and also includes first and last samples of the signal in the envelopes.
   
5. % inputs:
   
6. %   sig: vector of input signal
   
7. %   method: method of interpolation (defined as in interp1)
   
8. % outputs:
   
9. %   upperenv: upper envelope of the input signal
   
10. %   lowerenv: lower envelope of the input signal
    
11. function [upperenv lowerenv] = envelope(sig, method)
    
12. if nargin == 1
    
13.     method = 'linear';
    
14. end
    
15. upperind = find(diff(sign(diff(sig))) < 0) + 1;
    
16. lowerind = find(diff(sign(diff(sig))) > 0) + 1;
    
17. f = 1;
    
18. l = length(sig);
    
19. try
    
20.     upperind = [f upperind l];
    
21.     lowerind = [f lowerind l];
    
22. catch
    
23.     upperind = [f; upperind; l];
    
24.     lowerind = [f; lowerind; l];
    
25. end
    
26. xi = f : l;
    
27. upperenv = interp1(upperind, sig(upperind), xi, method, 'extrap');
    
28. lowerenv = interp1(lowerind, sig(lowerind), xi, method, 'extrap');
    
29. -----
    
30. 用法如
    
31. sig=[1 2 1 3 1 4 1 5 1 6 1 7 1 8 1 9 1 10 1 11];
    
32. envelope(sig,'linear')
    
33. 
    
34. ans =
    
35. 
    
36.   Columns 1 through 12
    
37. 
    
38.     1.0000    2.0000    2.5000    3.0000    3.5000    4.0000    4.5000    5.0000    5.5000    6.0000    6.5000    7.0000
    
39. 
    
40.   Columns 13 through 20
    
41. 
    
42.     7.5000    8.0000    8.5000    9.0000    9.5000   10.0000   10.5000   11.0000
    
43. [upperenv lowerenv] = envelope(sig, 'linear');
    
44. plot(sig);
    
45. hold on;
    
46. plot(upperenv); </font>

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转自：http://blog.sina.com.cn/s/blog_49c02a8c0100yt0y.html