samer@32: function R=spec2ac(A)
samer@32: % SPEC2AC - convert power spectrum to autocorrelation sequence
samer@32: %
samer@32: % assumes that S is a half-spectrum.
samer@32: % R=spec2ac(S)
samer@32: 
samer@32: if isvector(A), A=A(:); end
samer@32: 
samer@32: S=[A; A(end-1:-1:2,:)]; 
samer@32: R=real(ifft(S));					% autocorrelation
samer@32: R=R(1:(1+size(R,1)/2),:);		% extract  first half (rest is symmetric)
samer@32: