Inverse fast Fourier transform
Syntax: |
y = IFFT(m)
|
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.