An in-depth look at the derivation of the Discrete Fourier Transform (DFT) and the Fast Fourier Transform (FFT), along with an introduction to the FFTW library.
An in-depth look at the derivation of the Discrete Fourier Transform (DFT) from the Discrete-Time Fourier Transform (DTFT), including the sampling process and the final DFT and IDFT formulas.