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dwt3

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slama najla
slama najla 2012-4-20
hello, can some body help me to show the 4 subbands (approximation+ 3 subbands of details )getting from dwt3, because any code i find it give just the approximation + details and not the 4 subbands us in dwt2, please help me

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回答（2 个）

Wayne King
Wayne King 2012-4-20
Hi Slama, There are more than 4 subbands in the 3D discrete wavelet transform. There are 8 subbands. This are listed on the reference page for wavedec3
http://www.mathworks.com/help/toolbox/wavelet/ref/wavedec3.html
They are:
LLL,HLL,LHL,HHL,LLH,HLH,LHH,HHH
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slama najla
slama najla 2012-4-23
yes, i'm sorry i mean th 8 sub bands,but i can't arrive to to know how can i use only the mid frequencies(LHL and LLH) because it give A+D not
LLL,HLL,LHL,HHL,LLH,HLH,LHH,HHH.Thanks to help me please.

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Wayne King
Wayne King 2012-4-23
I'm not sure what you are asking. You can zero out everything in the output of wavedec3 except those subbands you are interested in, and then use waverec3 to reconstruct based on those subbands.
M = magic(8);
% Make data 3-D
X = repmat(M,[1 1 8]);
% Decompose X at level 1 using db1.
wd1 = wavedec3(X,1,'db1');
As it states in the documentation I referred you wd1.dec{3} and wd1.dec{5} contain the LHL and LLH subbands you wish.
So you can extract them directly
LHL = wd1.dec{3};
LLH = wd1.dec{5};
Or you can create an approximation to the data based on just these details and use waverec3.

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