create a iteration in a group

[cecily]

Here is the original data

class

1

1

1

1

1

1

3

3

3

4

4

4

4

And I would like to create a new variable which counts the number in each group.

class    count

1               1

1               2

1               3

1               4

1               5

1               6

3               1

3               2

3               3

4               1

4               2

4               3

4               4

I think I may use first. last.variable to get the count.But I still don't know how to write the code...Could you help me?

[Reeza · Accepted solution]

SAS FAQ: How can I create an enumeration variable by groups?

[cecily]

thank you very much