flagging duplicate values

[ari]

data:

ID	a	b
1	10	2
1	200	14.4
1	400	5
1	600	5

want:

ID	a	b	c (flag)
1	10	2	0
1	200	14.4	0
1	400	5	0
1	600	5	1

So,  variable b has same value 5 in rows 3 and 4. I need to flag first value (row 3)as 0 and subseqent rows containing value 5 as 1.

Thank you.

[jklaverstijn]

This is my 2 cents. Depending on what you'd like to do with variable a your final version can differ. But the use of first. will be my recommendation.

proc sort data=have;
   by id b;
run;
data want;
   set have;
   by id b;
   if first.b then c=0;
   else c=1;
run;

Regards,

- Jan.

[ari]

You code works but I need to flag only  one numeric value 5.  For instance, if there are duplicate 8 values , there is no need to flag

[jklaverstijn · Accepted solution]

How about this then:

proc sort data=have;
   by id b;
run;
data want;
   set have;
   by id b;
   c = 0;
   if not first.b and b=5 then c=1;
run;

- Jan

[ari]

Thanks. It works 

[jklaverstijn]

Good to hear. Glad to be of help. Please do not hesitate to flag the question as resolved.

Regards Jan.