View the speed comparison between the DFT and FFT algorithm:
To view the 'Fourier Transform - visual explanation.ggb' file, you need Geogebra, which you can download for free (https://www.geogebra.org/download - Classic recommended) or run in your browser (https://www.geogebra.org/classic).\ You can play around with the original signal (signal(x)), the cycling frequency f, the timevariable t (which also draws the wrapped signal and moves through the original signal) and also activate the points P, which are taken to compute the center point, as well as the corresponding points in the signal Pdisplay. And finally it displays (the real part of) the fourier transform in green.
For further information, take a look at:
http://www.falstad.com/fourier/ - Applet with interactive Fourier Series and Fourier Transform representation
https://www.youtube.com/watch?v=spUNpyF58BY - 3blue1brown: visual introduction to Fourier Transform
https://www.youtube.com/watch?v=mkGsMWi_j4Q - Simon Xu: step by step introduction to the DFT
https://www.youtube.com/watch?v=cUD1gMAl6W4 - GLV: Fourier Series Square Wave, a visual representation of Fourier Additive Synthesis\