getA.m

function A = getA( assigned_states )
%getA A is N*4 matrix, the 4 columns save the beginnings of S1, systole, S2 and diastole in the same heart cycle respectively
%% We just assume that the assigned_states cover at least 2 whole heart beat cycle
indx = find(abs(diff(assigned_states))>0); % find the locations with changed states

if assigned_states(1)>0   % for some recordings, there are state zeros at the beginning of assigned_states
    switch assigned_states(1)
        case 4
            K=1;
        case 3
            K=2;
        case 2
            K=3;
        case 1
            K=4;
    end
else
    switch assigned_states(indx(1)+1)
        case 4
            K=1;
        case 3
            K=2;
        case 2
            K=3;
        case 1
            K=0;
    end
    K=K+1;
end

indx2                = indx(K:end);
rem                  = mod(length(indx2),4);
indx2(end-rem+1:end) = [];
A                    = reshape(indx2,4,length(indx2)/4)'; % A is N*4 matrix, the 4 columns save the beginnings of S1, systole, S2 and diastole in the same heart cycle respectively

end