fftn (MATLAB Functions)

Multidimensional discrete Fourier transform

Syntax

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

Description

Y = fftn(X) returns the discrete Fourier transform (DFT) of X, computed with a multidimensional fast Fourier transform (FFT) algorithm. 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 execution time for fft depends on the length of the transform. It is fastest for powers of two. It is almost as fast for lengths that have only small prime factors. It is typically several times slower for lengths that are prime or which have large prime factors.

Note You might be able to increase the speed of fftn using the utility function fftw, which controls how MATLAB optimizes the algorithm used to compute an FFT of a particular size and dimension.

Data Type Support

fftn supports inputs of data types double and single. If you call fftn with the syntax y = fftn(X, ...), the output y has the same data type as the input X.

See Also

fft, fft2, fftn, fftw, ifftn

fft2 fftshift