Partial Fast Fourier Transform

Fast computation of part of an FFT using fractional fourier transform

This program uses the fractional fourier transform to compute only part of the FFT. It is even faster if the signal is sparse (i.e. it contains only a few non-zero elements).

Example:

signal=rand(16,1);
ft=FPFT(signal,1024,64);

This computes the first 64 points of the FFT of signal, signal is padded with zeroes to length 1024 first. This is much faster than

ft=FFT(signal,1024);ft=ft(1:64);

FPFT uses a caching mechanism to improve speed for multiple calls.