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numCoefficients

Number of wavelet scattering coefficients

Description

example

ncf = numCoefficients(sf) returns the number of scattering coefficients for each scattering path in the scattering framework sf. The number of scattering coefficients depends on the values of the SignalLength, InvarianceScale, and OversamplingFactor properties of sf.

Examples

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This example shows how to oversample a 1-D wavelet scattering transform.

Load an ECG signal sampled at 180 Hz, and create a wavelet scattering framework to process the signal. To perform a critically downsampled wavelet scattering transform, do not change the value of the OversamplingFactor property in sf. Return the number of scattering coefficients for the framework.

load wecg
Fs = 180;
sf = waveletScattering('SignalLength',numel(wecg),'SamplingFrequency',Fs);
ncf = numCoefficients(sf)
ncf = 8

Return the 1-D wavelet scattering transform of wecg, and plot the zeroth-order scattering coefficients. Confirm the number of zeroth-order scattering coefficients is equal to ncf.

s = scatteringTransform(sf,wecg);
display(['Number of zeroth-order scattering coefficients: ',...
  num2str(numel(s{1}.signals{1}))])
Number of zeroth-order scattering coefficients: 8
plot(s{1}.signals{1},'x-')
grid on
axis tight
title('Zeroth-Order Scattering Coefficients')

To oversample the scattering coefficients by a factor of 2, set the OversamplingFactor property of sf equal to 1 (because log22=1). Return the number of scattering coefficients for the edited framework. Confirm the number of scattering coefficients has doubled.

sf.OversamplingFactor = 1;
ncf = numCoefficients(sf)
ncf = 16

Return the wavelet scattering transform of wecg using the edited framework, and plot the zeroth-order scattering coefficients. Since the number of coefficients in the critically sampled transform is equal to 8, confirm that the number of zeroth-order coefficients in the oversampled transform is equal to 16.

s = scatteringTransform(sf,wecg);
figure
plot(s{1}.signals{1},'x-')
grid on
axis tight
title('Zeroth-Order Scattering Coefficients')

Input Arguments

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Scattering decomposition framework, specified as a waveletScattering object.

Introduced in R2019a