Patient Id = 1 , X, (days) = 381 , sigma = 0 Patient Id = 2 , X, (days) = 226 , sigma = 0 Patient Id = 3, X, (days) = 43 , sigma = 1 Patient Id = 4 X, (days) = 238 , sigma = 1 Patient Id = 5 , X, (days) = 111 , sigma = 0 Patient Id = 6, X, (days) = 149 , sigma = 1 Calculate Nelson Aalen estimate of the cumulative hazard function at t=230