## Copyright (C) 2006 Robert T. Short
## 
## usage:  [d]=delayCorrelate(d1,d2)
## 
## Estimate the delay between times series 'd1' and time series 'd2' by
## correlating and finding the peak.  The index of the peak correlation
## is returned in 'd'.
##
  
## Author:  Robert T. Short (address@hidden)
## Description:  Delay Correlate.
function [d,c]=delayCorrelate(d1,d2)

  % Check arguments and set defaults.

  if( (nargin<2) | (nargin>2) )
    usage('[d]=delayCorrelate(d1,d2)');
  end

  %  Make everything a column vector, then get the lengths.

  d1 = d1(:); d2 = d2(:);
  N1 = length(d1);     % total data length
  N2 = length(d2);     % 
  c = zeros(N2-N1+1,1);

  for (idx = 1:N2-N1)
    c(idx) = d1'*d2(idx:idx+N1-1)/N1;
  end
  [m,d] = max(abs(c));

end