function y = Disfrct(f,a,p)% Computes discrete fractional cosine transform% of order a of vector f% p (optional) is order of approximation, default N/2% S-C Pei, M-H Yeh, IEEE Tr SP 49(6)2001, pp.1198-1207N = length(f);shft = rem((0:N-1)+fix(N/2),N)+1;f = f(:);if (nargin==2), p = N/2; end;p = min(max(2,p),N-1);E = dFRCT(N,p);y=E*(exp(-j*pi*a*([0:N-1])).'.*(E'*f));function E=dFRCT(N,p)%function E=dFRCT(N,p) returns the NxN eigenvectors of the %Fourier Cosine transform matrixglobal EC_saved pC_savedif (length(EC_saved) ~= N | pC_saved ~= p),    E = make_EC(N,p);    EC_saved = E; pC_saved = p;else    E = EC_saved; end;function E = make_EC(N,p)% Returns sorted eigenvectors and eigenvalues of corresponding vectors% Construct matrix H, use approx order pN1=2*N-2;d2 = [1 -2 1]; d_p = 1; s = 0; st = zeros(1,N1);for k = 1:p/2,    d_p = conv(d2,d_p);    st([N1-k+1:N1,1:k+1]) = d_p; st(1) = 0;    temp = [1:k;1:k]; temp = temp(:)'./[1:2*k];    s = s + (-1)^(k-1)*prod(temp)*2*st;end;H = toeplitz(s(:),s)+diag(real(fft(s)));% Construct transformation matrix VV = [zeros(N-2,1),eye(N-2),zeros(N-2,1),flipud(eye(N-2))]/sqrt(2);V = [1,zeros(1,N1-1);V;zeros(1,N-1),1,zeros(1,N-2)];% Compute eigenvectorsEv = V*H*V';[ve,ee]=eig(Ev);% malab eig returns sorted eigenvalues% if different routine gives unsorted eigvals, then sort first% [d,inde] = sort(diag(ee));% ve = ve(:,inde');E = fliplr(ve);E(end,:) = E(end,:)/sqrt(2);