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Question about wavelet and reconstruction

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tanglaoya
tanglaoya 2016 年 9 月 20 日
コメント済み: tanglaoya 2016 年 10 月 6 日
Dear all, I am studying wavelet and focusing on the signal reconstruction. I noticed that the function 'upcoef' just work for the reconstruction: http://cn.mathworks.com/help/wavelet/ref/upcoef.html
At the end of this page, I also noticed that upcoef is equivalent to an N time repeated use of the inverse wavelet transform.
Then I tried to test it with the following code:
t=0:2*pi/999:2*pi;
b0=sin(t);
figure,plot(b0);
[cA,cD]=dwt(b0,'db4',3);
D = upcoef('d',cD,'db4',3,length(b0));
figure,plot(D);
[cA,cD]=dwt(b0,'db4');
[cA,cD]=dwt(cA,'db4');
[cA,cD]=dwt(cA,'db4');
D=idwt([],cD,'db4');
D=idwt([],D,'db4');
D=idwt([],D,'db4',length(b0));
figure,plot(D)
However, results by two methods are different. Could anyone tell me what's wrong in the code?
Thanks, Tang Laoya
  3 件のコメント
tanglaoya
tanglaoya 2016 年 9 月 20 日
Not only the roundoff error. I guess there is something wrong in the code. Thanks

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回答 (1 件)

Wayne King
Wayne King 2016 年 10 月 4 日
One problem you are having is that DWT does not take the 3 input you are using. DWT only does a single-level wavelet transform unlike wavedec. The 3 input to DWT above is NOT being used. It has no effect on the output.
  1 件のコメント
tanglaoya
tanglaoya 2016 年 10 月 6 日
Hi Wayne, Thanks for your kindly reply. I did use wavedec in my latter comment, but the results are the same.

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