Average columns together that share a common value

Lets say I have a 2 x 10 matrix M

The first column being an ID, and the second a value

1, 25

3, 33

3. 45

2, 22

4, 54

4, 56

5, 23

5, 65

1, 27

2, 29

How could I average the values with the same ID such that the new matrix would be

1, 26

2, 25.5

3, 39

4, 55

5, 44

Answer 1

[Paul]

D = [1, 25
3, 33
3. 45
2, 22
4, 54
4, 56
5, 23
5, 65
1, 27
2, 29];

[G,ID] = findgroups(D(:,1));
[ID splitapply(@mean,D(:,2),G)]

ans = 5×2

1.0000 26.0000 2.0000 25.5000 3.0000 39.0000 4.0000 55.0000 5.0000 44.0000