Smooth the SWDFT coefficients
smooth_swdft(a, ktype = "daniell", m = 2, num_convs = 1)
real or complex-valued swdft. If real-valued, then we assume it's the squared modules already. If it's complex valued, we convert to the squared modulus.
either 'daniell' or 'modified.daniell'
kernel width from stats::kernel
num_convs from stats::kernel
Smooth squared modulues SWDFT coefficients