# 7.00.02 - FFT - Aster Analytics

## Teradata Aster® Analytics Foundation User GuideUpdate 2

Product
Aster Analytics
Release Number
7.00.02
Release Date
September 2017
Content Type
Programming Reference
User Guide
Publication ID
B700-1022-700K
Language
English (United States)

The FFT function uses a Fast Fourier Transform (FFT) algorithm to compute the discrete Fourier Transform (DFT) of each signal in one or more input table columns. A signal can be either real or complex, and can have one, two, or three dimensions. If the signal length is not a power of two, the function either pads or truncates it to the closest power of two.

The DFT of a time sequence of length N, 0..N-1, is:
X(k) = Xk(N - k)

where k ϵ 0..N-1.

Therefore:
• The FFT of a time sequence of length 1 is the one-element sequence itself.
• The FFT of a time sequence of length 2 has only real values.
• The FFT of a time sequence of length 4 or greater has conjugate symmetry.

To recover the original signals, use the IFFT function.