how dwt and wavedec are different ? here why cA1 and C have diffrent values?

data=xlsread('E:\color\neha.xlsx');

data= data';

value1=data(1,:);

chan1= value1-mean(value1);

[cA1,cD1] = dwt(chan1,'db4');

[cA2,cD2] = dwt(cA1,'db4');

[cA3,cD3] = dwt(cA2,'db4');

[cA4,cD4] = dwt(cA3,'db4');

[cA5,cD5] = dwt(cA4,'db4');

[cA6,cD6] = dwt(cA5,'db4');

[cA7,cD7] = dwt(cA6,'db4');

[cA8,cD8] = dwt(cA7,'db4');

[cA9,cD9] = dwt(cA8,'db4');

[cA10,cD10] = dwt(cA9,'db4');

[C,L] = wavedec(chan1,10,'db4');

[Raul Souza Muniz]

Can I ask you something ? Do I have to do this manually. I mean, could I make an matrix and put all the c values and D values in the matrix with a for loop ? I cannot see a way to do this, because there is a long time since I programed in matlab. Really sorry for my dumb question.

Thank you very much

Answer 1

[Wayne King]

As you see, dwt() gives only a level 1 DWT, while wavedec gives you multiple levels. But you are correct that wavedec() simply iterates on the approximation coefficients of the previous level as expected.

Why do you say they are different? I do not see it. The first L(1) elements of wavedec should equal cA10 above

chan1 = randn(1024,1);
[cA1,cD1] = dwt(chan1,'db4');
[cA2,cD2] = dwt(cA1,'db4');
[cA3,cD3] = dwt(cA2,'db4');
[cA4,cD4] = dwt(cA3,'db4');
[cA5,cD5] = dwt(cA4,'db4');
[cA6,cD6] = dwt(cA5,'db4');
[cA7,cD7] = dwt(cA6,'db4');
[cA8,cD8] = dwt(cA7,'db4');
[cA9,cD9] = dwt(cA8,'db4');
[cA10,cD10] = dwt(cA9,'db4');
[C,L] = wavedec(chan1,10,'db4');

Now compare:

   C(1:L(1))

with

   cA10

Likewise, compare

C(L(1)+1:L(1)+L(2))

with

cD10

[amit_neuro]

thanks King. i got it.

But tell me on more thing, "is it necessary to reconstruct the cA10 to get the real signal?"

[Wayne King]

It's only necessary if you have gone down to that level in the multiresolution analysis, if you go down to level 10, then you need the the final level approximation coefficients to achieve perfect reconstruction.

Answer 2

[TONY SINGLA]

hello

i have a doubt that how DWT calculates the values for the cd1,ca1 and cd2,ca2 and so on............... which *|formula |*it uses to calculate the values for the respective C and L values in case of 1D-DWT at multilevel

reply please waiting for your reply

Answer 3

[Murugesh]

you refer waverec