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Littlewood-Paley sum

returns the Littlewood-Paley sum for the scattering filter banks in `lpsum`

= littlewoodPaleySum(`sf`

)`sf`

,
the wavelet time scattering network. `lpsum`

is an
*M*-by-*L* matrix, where *M* is the
number of elements in the Fourier transform of the scattering filters, and
*L* is the number of scattering filter banks. The columns of
`lpsum`

are ordered by the position of the filter bank in the
scattering network. For example, the first column of `lpsum`

corresponds
to the filter bank used for the first-order scattering coefficients.

Since the scattering transform is contractive, the Littlewood-Paley sums will not exceed one.