Discrete Fourier transform - Wikipedia
https://en.wikipedia.org/wiki/Discrete_Fourier_transformThe DFT has seen wide usage across a large number of fields; we only sketch a few examples below (see also the references at the end). All applications of the DFT depend crucially on the availability of a fast algorithm to compute discrete Fourier transforms and their inverses, a fast Fourier transform. When the DFT is used for signal spectral analysis, the sequence usually represents a finite set of …