function y = acf2(x, range, windowsize)
% y=acf2(x,range,windowsize) - running autocorrelation function 
% range and windowsize are in samples
% fixed window is at end of input array, moving window slides back

N = size(x,2);
if (range+windowsize>= N)
	error('range+windowsize larger than input array');
end;
y = zeros(size(x,1) ,range);


z = x(:, N-windowsize+1:N);	% fixed window
for i = 0:range-1
	zz = x(:, N-windowsize+1-i: N-i);	% sliding window
	zzz = sum(z' .* zz');
	y(:,i+1) = zzz';
end