function S=phasespec(X)
% PHASESPEC(X): get phase spectra of columns of x
%
% phasespec :: [[N,T]->real] -> [[M,T]->complex]] :- M is N/2+1.

m=size(X,1)/2;
S=fft(X);
S=S(1:m+1,:)./abs(S(1:m+1,:)); % get complex phases of components.
% first and last rows should be ones

