Count changes in column (lag function)

[PatrykSAS]

I would like to count value changes in a column like below:

ID	VALUE	COUNT
1	10	0
1	10	0
1	12	1
1	15	1

In this example ID and VALUE is my data and I want to make count column equal 1 each time the value change in given ID

I heard about lag function which could be helpful but I am not sure how to use it

[Ksharp · Accepted solution]

data have;
input ID	VALUE;
cards;
1	10	
1	10	
1	12	
1	15
;
data want;
 set have;
 by id value notsorted;
 count=first.value;
 if first.id then count=0;
run;

[FreelanceReinh]

Hi @PatrykSAS,

---

@PatrykSAS wrote:

I heard about lag function which could be helpful but I am not sure how to use it

---

Here's how the LAG function could be used:

data want;
set have;
count = value~=lag(value) & id=lag(id);
run;