How can I reconstruct the details and approximation after using 'swt' (stationary wavelet decomposition) of the wavelet toolbox?

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Hi, I am currently using ‘swt’ of the wavelet toolbox to obtain a stationary wavelet decomposition of a signal. Is there a similar command to 'wrcoef' to reconstruct the details and approximation? Best. Marie

Answers (1)

Wayne King
Wayne King on 5 May 2016
Hi Marie, Not directly for SWT, but there is a work around. Let me say however, that starting in R2015b there is MODWT-MODWTMRA that implements an undecimated discrete wavelet transform for arbitrary length time series and that does directly provide an equivalent for wrcoef.m
Here is the work around for SWT -- Let's assume you want D3
load wecg;
swc = swt(wecg,8,'sym4');
swctmp = zeros(size(swc));
swctmp(3,:) = swc(3,:);
D3 = iswt(swctmp,'sym4');
Now here is the MODWT-MODWTMRA way
wt = modwt(wecg); % 'sym4' is default wavelet
mra = modwtmra(wt);
d3 = mra(3,:);
Let's compare D3 and d3
I would recommend the MODWT-MODWTMRA way because that is more exactly what you want.

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