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clear
defaults
!
DEFINE\CONSTANTS ! define pi (among other constants)
N = 16 ! even number of points
X = [0:N-1]*2*PI/N ! generate some "data"
Y = SIN(X)+5*RAN(X) !
M = FFT(Y,'COS&SIN') ! calculate Fourier coefficients
H = M[*,1] ! extract column 1 as a vector
G = M[*,2] ! extract column 2 as a vector
Z = [0:2*PI:.05]
DO J = [3:N/2+1:2]
WINDOW (J-3)/2+5 ! choose a graphics window
DEFAULTS
SCALE\-mess 0 6 0 -2 7 0 ! set axis scales
SET
PLOTSYMBOL -1 ! choose plotting symbol
%XNUMBERSHEIGHT 5
%YNUMBERSHEIGHT 5
GRAPH X Y ! plot original data
SET PLOTSYMBOL 0 ! choose no plotting symbol
TMP[1:LEN(Z)] = 0
DO K = [2:J]
TMP = TMP + H[K]*COS((K-1)*Z)+G[K]*SIN((K-1)*Z)
ENDDO
GRAPH\OVERLAY Z H[1]/2+TMP
DESTROY\-mess TMP
SET
%TEXTHEIGHT 5 ! increase the size of the x-axis label
%XTEXTLOCATION 50
%YTEXTLOCATION 80
TEXTALIGN 2
TEXTINTERACTIVE 0
TEXT RCHAR(J)//' harmonics used'
replot
ENDDO
GRAPH\OVERLAY [0;2*PI] [H[1]/2;H[1]/2] ! overlay the mean value
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