function cycplot(s,a,e)%function cycplot(s,a,e)%%To plot a Fourier transform as a three dimensional cyclic%plot (see Bracewell "The Fourier Transform and its%Applications," p363.%           s = Fourier transform of something (the real part%               is used)%           a = azimuth of viewpoint%           e = elevation of viewpoint%%                   Andrew Knight June 1991;s = real(s);[m,n] = size(s);if min(m,n)>1   error('s must be a vector.')elseif m>1   s = s';endxx = [1:n ; 1:n];yy = [zeros(1:n) ; s];theta = linspace(-pi/2,3*pi/2,n + 1);theta = theta(1:n);x3d = cos(theta);y3d = sin(theta);[Y,Z] = rota3d(x3d,y3d,yy(2,:),a,e);[Yzero,Zzero] = rota3d(x3d,y3d,zeros(1:n),a,e);YY = [Yzero ; Y];ZZ = [Zzero ; Z];%Axes:xax = [1 -1 0 0];yax = [0 0 1 -1];zax = [0 0 0 0];[Yax,Zax] = rota3d(xax,yax,zax,a,e);Yax = reshape(Yax,2,2);Zax = reshape(Zax,2,2);%Base circle:theta = linspace(0,2*pi,200);xcirc = cos(theta);ycirc = sin(theta);zcirc = zeros(xcirc);[Ycirc,Zcirc] = rota3d(xcirc,ycirc,zcirc,a,e);M_ax = max(max(Zax,Yax));m_ax = min(min(Zax,Yax));M_circ = max(max(Zcirc,Ycirc));m_circ = min(min(Zcirc,Ycirc));M_ZY = max(max(Z,Y));m_ZY = min(min(Z,Y));M = max([M_ax,M_circ,M_ZY]);m = min([m_ax,m_circ,m_ZY]);axis([m M m M])hold onplot(Zax,Yax,'g-',...     Zcirc,Ycirc,'b-',...     ZZ,YY,'c12-',Z,Y,'c5o')		 hold off