MATLAB: How to normalize a signal to zero mean and unit variance

ehg signalWavelet Toolboxwavelets

i'm trying to normalize EHG signal's wavelet components to zero mean and unit variance,and i have used

 cA3=reshape(zscore(cA3(:)),size(cA3,1),size(cA3,2));

this matlab expression,and got an answer like this

>> mean2(cA3(:))
ans =
       -2.84121591248158e-16
  >> var(cA3(:))
ans =
                           1

Best Answer

Those values are normalized. The 1e-16 is due to limitations in floating point calculation

Related Solutions

MATLAB: How dwt and wavedec are different ? here why cA1 and C have diffrent values

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

MATLAB: Do the values of the length of DWT2 coefficients for different modes (as specified in the help) differ from the actual formula

This enhancement has been incorporated in Release 2008b (R2008b). For previous product releases, read below for any possible workarounds:

This is an error in the documentation. In the help page for the function DWT2, the following is stated:

Let sx = size(X) and lf = the length of filters; then size(cA) = size(cH) = size(cV) = size(cD) = sa

where sa = ceil(sx/2), if the DWT extension mode is set to periodization. For the other extension modes, sa = floor((sx+lf-1)/2).

It should actully read as:

Let sx = size(X) and lf = the length of filters; then size(cA) = size(cH) = size(cV) = size(cD) = sa

where sa = ceil(sx/2), if the DWT extension mode is set to symmetric padding . For the other extension modes, sa = floor((sx+lf-1)/2).

Note: The difference is, in the DWT Extension mode should be specified as a "symmetric padding".

Best Answer

Related Solutions

MATLAB: How dwt and wavedec are different ? here why cA1 and C have diffrent values

MATLAB: Do the values of the length of DWT2 coefficients for different modes (as specified in the help) differ from the actual formula

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