How to map a set of integer IDs to serial natural numbers?

Hello,

I'm trying to map a set of IDs which are integers to a list of serial numbers. So, for example, the IDs are as follows:

[12 13 20 12 5 12 13]

then the output should be

[2 3 4 2 1 2 3]

Thus, 5 has been mapped to 1 and 20 has been mapped to 4.

Is there a clever and efficient way to accomplish this? I believe the command 'unique' should help, but I'm not able to find a way to use it.

Answer 1

[Walter Roberson]

[u,a,b] = unique([12 13 20 12 5 12 13]);

and then b is the vector you want.

[Saurabh]

Now I feel like an idiot for not reading the documentation on unique carefully.

Thanks, that was fast!