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Topic: Please correct the energy
Replies: 3   Last Post: Oct 28, 2010 5:55 PM

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Wayne King

Posts: 2,961
Registered: 4/1/09
Re: Please correct the energy
Posted: Oct 28, 2010 5:55 PM
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"Dinesh Bhati" <bhatidinesh@gmail.com> wrote in message <ia8cs1$n7e$1@fred.mathworks.com>...
> Hi,
>
> Can any one correct the energy Emid. It should also be same as Ex and Ey and equal to one.Note for DB1 you will get the correct Emid.
>
> clear
> clc
> str='db2'
> x=randint(1,10,[1 10]);
> x=x/norm(x(:));
> Ex=sum(x.^2)
> [A,H]=dwt(x,str);
> Emid=sum(A.^2)+sum(H.^2)
> y=idwt(A,H,str);
> Ey=sum(y.^2)
>
> Dinesh


Hi Dinesh, The problem is you should set the dwtmode() to 'per'. If the dwtmode() is the default value of 'sym', the pythagorean theorem for the orthogonal decomposition of the signal into the approximation and detail coefficients will not hold. Also, you should use randi()--randint is obsolete.

dwtmode('per','nodisplay')
reset(RandStream.getDefaultStream);
str = 'db2';
r = randi(10,10,1);
r = r./norm(r,2);
[A,H]=dwt(r,str);
norm(A,2)^2+norm(H,2)^2

% ans = 1.0000

Hope that helps,
Wayne



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