Discrete wavelet transform-wavedec

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Hai Tran
Hai Tran 2016년 5월 10일
답변: Asfaw Alem 2022년 7월 28일
Dear all, Could you please answer my question? First, I use [C,L]=wavedec(signal(1024x1),m(1:10),'haar') (Eq.1) to find cD1 (512x1),cD2(256x1)... after that, i want to check how does wavedec function work? And i try with haar=[1/sqrt(2) -1/sqrt(2)](for example m=1) and apply cD1'=conv(signal,haar) (2). Eq.(2) gave me cD1'= minus(cD1) in Eq.1 (I just talk about value) Why is there difference between wavelet coefficients in Eq1 VS.Eq.2 ?
Thank you so much for your consideration to my question

채택된 답변

Wayne King
Wayne King 2016년 5월 10일
Hi Hai,
The Haar high pass analysis filter used in DWT() which is called by WAVEDEC() is
[-1/sqrt(2) 1/sqrt(2)]
To demonstrate the equivalence between convolution as implemented by conv() and the wavelet transform, you should set the DWTMODE to 'per'
Lo = [1/sqrt(2) 1/sqrt(2)];
Hi = [-1/sqrt(2) 1/sqrt(2)];
% generate a test signal
x = randn(16,1);
[A,D] = dwt(x,'haar');
% Now compare A to
% Compare D to
  댓글 수: 1
Hai Tran
Hai Tran 2016년 5월 11일
Thank you so much Dr.Wayne King

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Asfaw Alem
Asfaw Alem 2022년 7월 28일
how can plot PAPR for haar wavelet


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