id = [1004, 1004, 1004, 1004]';
length = [23, 45, 56, 78]';
N = [1, 4, 2, 1]';
T = table(id, length, N)
id2 = [1004, 1004, 1004, 1004, 1004, 1004, 1004, 1004]';
length2 = [23, 45, 45, 45, 45, 56, 56, 78]';
N2 = [1, 1, 1, 1, 1, 1, 1, 1]';
T2 = table(id2, length2, N2)