This short m-file demonstrates the Gibbs' phenomenon in Signal Processing.
It clearly shows the "ringing" when the number of Fourier components are enhanced while synthesising a square waveform.
You can see that the periodicity of the sidelobes depends on the N. Lanczos realizes this and performed a running mean over them as width as this periodicity reducing this phenomena and inventing the Lanczos Filter.
I reccomend you to include comments in your file or something interesting, if it will be only a demo. Otherwise this one is incredibly much better:
Download apps, toolboxes, and other File Exchange content using Add-On Explorer in MATLAB.