; Graphic demo of Gibbs phenomenon.
; Fourier series convergence is slowest near discontinuities.

; the function
 f(x) := SUM(SIN((2n+1)x)/(2n+1),n,0,20)*4/PI

; the domain for the plot
 GBOUNDS 0, PI
 PLOT f

; Some commands which make the plot look nicer.
 GSTYLE 1
 GPOINTS 100
 TITLE     "Gibbs phenomenon"
 SUBTITLE  "for the square wave"
 YLABEL    "20 Fourier terms"