function isicorr = isiserialcorr(isivec, maxlag)
% serial correlation of interspike intervals
%
% isicorr = isiserialcorr(isivec, maxlag)
%
% Arguments:
%   isivec: vector of interspike intervals in seconds
%   maxlag: the maximum lag in seconds
%
% Returns:
%   isicorr: vector with the serial correlations for lag 0 to maxlag

    lags = 0:maxlag;
    isicorr = zeros(size(lags));
    for k = 1:length(lags)
        lag = lags(k);
        if length(isivec) > lag+10        % ensure "enough" data
	    % NOTE: the arguments to corr must be column vectors!
            % We insure this in the isis() function that 
            % generates the isivec.
            isicorr(k) = corr(isivec(1:end-lag), isivec(lag+1:end));
        end
    end
    
    if nargout == 0
        % plot:
        plot(lags, isicorr, '-b');
        hold on;
        scatter(lags, isicorr, 10.0, 'b', 'filled');
        hold off;
        xlabel('Lag k')
        ylabel('\rho_k')
    end
end