Fourier Transform has been a widely used technique for extracting frequency information from temporal data. But I always wonder how does it work? What makes the FT has such a magical capability?
I thought about FT again yesterday and searched for some online resources. Here is a straightforward explanation of the principle of FT:
The Wavelet Tutorial Part 2 by Robi Polikar
I have to say: The idea of FT is really brilliant. Maybe this is something called ``the beauty of mathematics?'' :-)
DFT, FFT by Paul Bourke (with C code examples)
FFT in Python by Yukuan (in Chinese)
Discrete Fourier transform by Jang (some content presetnted in Chinese)