How to filter odd dates

[Ajayvit]

Hi Team,

I need help for below scenario.

All dated will be in ascending order and if any date is smaller than its previous date then that is odd and need to be filter out.

I applied lag function but it is getting applied on entire variable not on group if 1 and 2 separately.

data test1;
input id date$12.;
datalines;
1 01JAN2010
1 04JAN2010
1 08JAN2010
1 07JAN2010
1 11JAN2010
2 05JAN2010
2 06JAN2010
2 04JAN2010
2 07JAN2010
2 10JAN2010
;
RUN;

Expected output:

1 07JAN2010

2 04JAN2010

[Kurt_Bremser · Accepted solution]

Before doing anything else, convert the strings to SAS dates by using the INPUT function with the DATE9. informat.

Then it's easy:

data want;
set test1;
by id;
if date lt lag(date) and not first.id;
run;