function [ ind ] = onoffset( interval,mode )

%Function calculates on/off set of QRS complexe

slope = [];

for i = 2:length(interval)-1

    slope(end+1) = interval(i+1)-interval(i-1);

end

%   using MIN_SLOPE determine onset placement

if strcmp(mode,'on')

    [m,ind] = min(abs(slope));

    %display('onset detected');

elseif strcmp(mode,'off')

    slope_th = 0.2*max(abs(slope));

    slope_s = find(abs(slope)>=slope_th);

    ind = slope_s(1);

else

    display('wrong input, please select on/off set')

end

end