Using first. to add a count unique by two variables

[angel2]

How can I use a data step to create a count unique by ID and category. I want the same count to remain for non unique values. Please see example attached and the wanted counts. Thanks

[novinosrin · Accepted solution]

data have;
input (ID	CATEGORY) ($);*		WANTED COUNT;
cards;
001	PIG		1
001	PIG		1
003	SHEEP		1
003	PIG		2
003	PIG		2
004	SHEEP		1
004	SHEEP		1
005	PIG		1
005	PIG		1
005	COW		2
005	SHEEP		3
;

data want;
 set have;
 by id category notsorted;
 if first.id then count=1;
 else if first.category then count+1;
run;

[RichardDeVen]

Presuming the data is grouped into contiguous blocks the syntax BY var1 var2 NOTSORTED; can be used.  This assumption is made because group 5 is not sorted in alphabetical order.

data have; input
ID  CATEGORY $  wanted; datalines;
001  PIG        1
001  PIG        1
003  SHEEP      1
003  PIG        2
003  PIG        2
004  SHEEP      1
004  SHEEP      1
005  PIG        1
005  PIG        1
005  COW        2
005  SHEEP      3
;

data want;
  set have;
  by id category notsorted;
  if first.id then seq=0;
  if first.category then seq+1;
run;

Output

[angel2]

Thank you so much - that's perfect!