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7 votes
Accepted

Why does a signal with constant frequency have spots that changes colors at a specific value of scale (and so frequency) in the scalogram?

Re: real part There are oscillations because that's what the wavelet transform is - a decomposition into zero-mean, localized oscillations. CWT is convolution (rather, cross-correlation) of signal ...
OverLordGoldDragon's user avatar
4 votes
Accepted

PyWavelets CWT: normalization? Vs Scipy?

Let's follow the math from incubation to delivery. It begins with psi, a rescaled morlet2 (as shown previously) at a scale $a=64$...
OverLordGoldDragon's user avatar
3 votes
Accepted

How is wavelet center frequency computed?

Short version: DFT's bin indices are input length-dependent; "center frequency" is measured relative to the function generating the wavelet. Generated length can vary, so must be accounted ...
OverLordGoldDragon's user avatar
1 vote

Is there a reason why wavelet in continuous wavelet transform are symmetric?

Continuous wavelets do not need to be symmetric. Due to their high redundancy, mathematical conditions for a function to be an admissible wavelet are quite mild. In a nutshell, integrability, zero-...
Laurent Duval's user avatar
1 vote

Python's equivalent of MATLAB's cwtfilterbank

Avoid PyWavelets and scipy. ssqueezepy's (disclaimer, am author) scales='auto' is motivated similar to MATLAB's cwtfilterbank, ...
OverLordGoldDragon's user avatar
1 vote
Accepted

PyWavelets CWT implementation

First see "Naive Breakdown" in a below section. Onto PyWavelets: the algorithm was found on Github to stem from an old MATLAB implementation, but it provides no details on coding the wavelet ...
OverLordGoldDragon's user avatar
1 vote
Accepted

Discrete wavelet decomposition over detail coefficients

Indeed, that will be called a wavelet packet. No, you will split the cD3 band in two equal parts: $[Fs/16,3Fs/32]$ and $[3Fs/32,Fs/8]$ as you mentioned. Warning though, the frequency bin you ...
Laurent Duval's user avatar
1 vote

Pywavelets applied to time series

For DWT, the original signal is downsampled by a factor of two at each level of decomposition. It's based on filter banks, in which data is downsampled by a factor of 2, i.e., by a low pass filter - ...
humblefool_9's user avatar
1 vote

How to do appcoef and detcoef using pyWavelets?

From the matlab docs https://www.mathworks.com/help/wavelet/ref/appcoef2.html the appcoef function does: "If N = NMAX, then a simple extraction is done; otherwise, appcoef2 computes iteratively ...
user2561747's user avatar
1 vote
Accepted

How to plot the shape of a 2D wavelet?

Transform to time domain Center Plot real & imag separately, or use complex colormap, or take modulus Results below. Minimal code ...
OverLordGoldDragon's user avatar
1 vote

PyWavelets SWT versus MODWT

The answer to your question can be found here : https://github.com/PyWavelets/pywt/issues/600
Jokerp's user avatar
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