function dk=fsderiv(kn,wo)%FSDERIV Fourier Series Derivative.% FSDERIV(Kn,Wo) returns the FS coeficients of the derivative% of f(t) whose FS coeficients are given by Kn and whose% fundamental frequency is Wo rad/s.% If Wo is not given, Wo=1 is assumed.% D.C. Hanselman, University of Maine, Orono, ME 04469% 1/12/95% Copyright (c) 1996 by Prentice-Hall, Inc. if nargin==1,wo=1;endn=(length(kn)-1)/2;        % number of harmonicsdk=wo*sqrt(-1)*(-n:n).*kn; % jn*Wo*Kn is derivative