[y,varargout]=xcorAlign(x)

function [y,varargout]=xcorAlign(x)
% Aligns data according to cross correlation maximum.
% [y,varargout]=xcorAlign(x,varargin)
%
% USAGE:
% [dataout,lagout]=xcorAlign(data);
% 
% If only 1 output is specified, then dataout (a matrix the same size as
% data) is returned.
%
% INPUT:
% data: a matrix of data vectors stored column-wise.
%
% OUTPUT: 
% y: A matrix size(data) back.
% lagout: Optional.  A vector of lag indices.  These give the amount the 
%         column vectors of dataout are shifted with respect to the first 
%         column of data.
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

[M,N]=size(x);
y=x;
lagout=zeros(N,1);

%make infs zeros for computing purpose
x(isinf(x)) = 0;

%align against the first column vector

ftx1 = fft(x(:,2:end));
ftx2 = fft(x(:,1));

for k=2:N
    
    xc          = ifft(conj(ftx1(:,k-1)).*ftx2);
    [m,i]       = max(abs(xc));
    y(:,k)      = circshift(x(:,k),i);
    lagout(k)   =i;
    
end;
    
%asign output values
if(nargout==2);
    varargout{1}=lagout;
end;