Convolve two N-dimensional arrays using FFT. See convolve.
for use with arma (old version: in1=num in2=den in3=data
copied from scipy.signal.signaltools, but here used to try out inverse filter doesn’t work or I can’t get it to work
2010-10-23 looks ok to me for 1d, from results below with padded data array (fftp) but it doesn’t work for multidimensional inverse filter (fftn) original signal.fftconvolve also uses fftn