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I'm trying out PyWavelets and following this example. 

import pywt
x = [3, 7, 1, 1, -2, 5, 4, 6]
cA, cD = pywt.dwt(x, 'db2')

Just to confirm, is cA the scaling and cD the time delay? Any way to change shift/scale step (a and b parameters from wikipedia)?

ali_m
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Bobo
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1 Answers1

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No, cA and cD represent the Approximation and Detail coefficients respectively which are obtained after applying the discrete wavelet transform to the signal x.

The scaling and time delay which you are referring to are implicitly modelled when implementing the discrete wavelet transform via a digital filter bank.

  • By applying repeated decompositions of the approximation signal cA one implicitly varies the scale of the wavelet function used a
  • The time delay you refer to can be controlled by the order of the filter
Sjoerd
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