give a id to same values in a cell

i have a cell with values

   {'aa', 'aa', 'ab' ,'ab', 'ab', 'ac', ac', 'ad'};

now i want to give a number to same words eg:

[1 1 2 2 2 3 3 4];

please can someone help me...

Answer 1

[Stephen23]

You can use unique:

>> C = {'aa', 'aa', 'ab' ,'ab', 'ab', 'ac', 'ac', 'ad'};
>> [~,~,idx] = unique(C)
idx =
   1   1   2   2   2   3   3   4