function [A,B]=tpcoeff(X,Y,M)%Input    - X is a vector of equally spaced abscisssas in [-pi, pi]%         - Y is a vector of ordinates%         - M is the degree of the trigomometric polynomial%Output   - A is a vector containing the coefficients of cos(jx)%         - B is a vector containing the coefficients of sin(jx)%  NUMERICAL METHODS: Matlab Programs% (c) 2004 by John H. Mathews and Kurtis D. Fink%  Complementary Software to accompany the textbook:%  NUMERICAL METHODS: Using Matlab, Fourth Edition%  ISBN: 0-13-065248-2%  Prentice-Hall Pub. Inc.%  One Lake Street%  Upper Saddle River, NJ 07458N=length(X)-1;max1=fix((N-1)/2);if M>max1   M=max1;endA=zeros(1,M+1);B=zeros(1,M+1);Yends=(Y(1)+Y(N+1))/2;Y(1)=Yends;Y(N+1)=Yends;A(1)=sum(Y);for j=1:M   A(j+1)=cos(j*X)*Y';   B(j+1)=sin(j*X)*Y';endA=2*A/N;B=2*B/N;A(1)=A(1)/2;