Discrete wavelet transform-wavedec

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Hai Tran
Hai Tran el 10 de Mayo de 2016
Respondida: Asfaw Alem el 28 de Jul. de 2022
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

Respuesta aceptada

Wayne King
Wayne King el 10 de Mayo de 2016
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'
dwtmode('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
dyaddown(conv(x,Lo))
% Compare D to
dyaddown(conv(x,Hi))

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Asfaw Alem
Asfaw Alem el 28 de Jul. de 2022
how can plot PAPR for haar wavelet

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