Command invfft performs the inverse Fourier transform of the
given vectors. It assumes that the frequencies are ordered from 0 to
N/2 followed by negative frequencies ranging from - (N - 1)/2 to -1
in units of
1/(N*Δ) where Δ is the sampling interval.
The results are normalized by a factor
1/ so that a
transform followed by an inverse transform should give the original
vector. The resulting vectors are stored in the third and fourth
arguments. Thus, invfft X Y V W inverse transforms X+iY into
V+iW. Input vectors can be used as output vectors. See fft for
more details.
invfft real-VECTOR ima-VECTOR real-VECTOR ima-VECTOR
fft, smooth, cmode, let, read, math, data