# How to calculate the energy of details and approxmiations coefficients of discret wavelet transform ?

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afef on 20 Jul 2017
Commented: Mohan Das on 8 Dec 2022
Hi everyone, i calculate the energy of details and approxmiations coefficients of discret wavelet transform .i used DWT(Daub4) Here is the code
for n=1:23
deriv=(val(n,:))/2.559375;
t=(0:length(deriv)-1)/Fs;
result{n} = filtfilt(d1,deriv);
[c,l]=wavedec(result{n},4,'db4');
[cd1,cd2,cd3,cd4]=detcoef(c,l,[1,2,3,4]);
cA4=appcoef(c,l,'db4',4);
[Ea,Ed]=wenergy(c,l)
energie{n} = {Ea, Ed};
end
And when i was looking for the formula of the energy i found this : and as i understand the energy is the percentage of energy corresponding to the approximation and the details
So when i was trying to write a C code using this formula and the values of cd1,cd2,cd3,cd4 i don't get the same values that i have with matlab So i want to know where i wrong ?
i mean to calcuate the energy i should use [cd1,cd2,cd3,cd4]??
##### 2 CommentsShowHide 1 older comment
Mohan Das on 8 Dec 2022
sir kindly clarify first 4 line

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