Matlab - a command to sort variables into groups and output the group indices

Question

I have a vector, for example: a = [1 1 2 2 7 7 7 10 10 10 10 11 15]. It can be unsorted, but here I\'m writing it as sorted. I am looking for a Matlab command that will convert

Answer 1

There's at least two ways to do this

(1) use the third output of unique:

[~,~,out] = unique(a)

(2) use grp2idx from the statistics toolbox

out = grp2idx(a)