N-D inverse fast Fourier transform
Y = ifftn(X)
Y = ifftn(X,siz)
y = ifftn(..., 'symmetric')
y = ifftn(..., 'nonsymmetric')
ifftn tests X to see whether it is conjugate symmetric. If so, the computation is faster and the output is real. An N1-by-N2-by- ... Nk array X is conjugate symmetric if
X(i1,i2, ...,ik) = conj(X(mod(N1-i1+1,N1)+1, mod(N2-i2+1,N2)+1, ... mod(Nk-ik+1,Nk)+1))
for each element of X.
ifftn supports inputs of data types double and single. If you call ifftn with the syntax y = ifftn(X, ...), the output y has the same data type as the input X.
For any X, ifftn(fftn(X)) equals X within roundoff error.
ifftn(X) is equivalent to
Y = X; for p = 1:length(size(X)) Y = ifft(Y,,p); end
This computes in-place the one-dimensional inverse DFT along each dimension of X.
The execution time for ifftn 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 ifftn using the utility function fftw, which controls how MATLAB® software optimizes the algorithm used to compute an FFT of a particular size and dimension.