Inverse fast Fourier transform

Syntax: y = IFFT(m)
y = IFFT(m,'AMP&PHASE')
y = IFFT(m,'COS&SIN')

The IFFT function calculates the inverse discrete Fourier transform of the two column input matrix. This matrix is usually calculated by the FFT function, thus reconstructing the original data.

By default, IFFT expects amplitudes and phases, where the phases are in degrees. The first column of the matrix should contain the amplitudes and the second column the phases. If the COS&SIN keyword is used, IFFT expects the Fourier coefficients, that is, the cosine coefficients in the first column and the sine coefficients in the second column. If the input matrix has N rows, the function returns a vector with length 2(N-1).

The principle usage of the IFFT function is to modify some of the amplitudes returned from the FFT function and note their effect on the original data. A typical application would be one of data smoothing, in which the user would zero out the amplitudes of the higher order harmonics.