fftn (MATLAB Function Reference)

Multidimensional fast Fourier transform

Y = fftn(X)
Y = fftn(X,siz)

Description

Y = fftn(X)

performs the N-dimensional fast Fourier transform. The result Y is the same size as X.

Y = fftn(X,siz)

pads X with zeros, or truncates X, to create a multidimensional array of size siz before performing the transform. The size of the result Y is siz.

Algorithm

fftn(X) is equivalent to

Y = X;
for p = 1:length(size(X))
    Y = fft(Y,[],p);
end

This computes in-place the one-dimensional fast Fourier transform along each dimension of X. The time required to compute fftn(X) depends strongly on the number of prime factors of the dimensions of X. It is fastest when all of the dimensions are powers of 2.