function fano( spikes )
% computes fano factor as a function of window size
% spikes: a cell array of vectors of spike times

    tmax = spikes{1}(end);
    windows = 0.01:0.05:0.01*tmax;
    mc = windows;
    vc = windows;
    ff = windows;
    fs = windows;
    for j = 1:length(windows)
        w = windows( j );
        % collect counts:
        n = [];
        for k = 1:length(spikes)
            for tk = 0:w:tmax-w
                nn = sum( ( spikes{k} >= tk ) & ( spikes{k} < tk+w ) );
                %nn = length( find( ( spikes{k} >= tk ) & ( spikes{k} < tk+w ) ) );
                n = [ n nn ];
            end
        end
        % statistics for current window:
        mc(j) = mean( n );
        vc(j) = var( n );
        ff(j) = vc( j )/mc( j );
        fs(j) = sqrt(vc( j )/mc( j ));
    end
    
    subplot( 1, 2, 1 );
    scatter( mc, vc, 'filled' );
    xlabel( 'Mean count' );
    ylabel( 'Count variance' );

    subplot( 1, 2, 2 );
    scatter( 1000.0*windows, fs, 'filled' );
    xlabel( 'Window W [ms]' );
    ylabel( 'Fano factor' );
end