Compare number of instances in a column for two different dates in SAS - date

Question

I have the following dataset (items) with transactions on any date and amount paid on the next business day.
The amount paid for each id on the next business day is $10 for the ids whose rate is >5
My task is to compare the number of instances where rate > 5 are in line with amount paid on the next business day (This will have a standard code 121)
For instance, there are four instances with rate > 5 on 4/14/2017' - The amount$40 (4*10)is paid on4/17/2017`
Date id rate code batch
4/14/2017 1 12 100 A1
4/14/2017 1 2 101 A1
4/14/2017 1 13 101 A1
4/14/2017 1 10 100 A1
4/14/2017 1 10 100 A1
4/17/2017 1 40 121
4/20/2017 2 12 100 A1
4/20/2017 2 2 101 A1
4/20/2017 2 3 101 A1
4/20/2017 2 10 100 A1
4/20/2017 2 10 100 A1
4/21/2017 2 30 121
My code
proc sql;
create table items2 as select
count(id) as id_count,
(case when code='121' then rate/10 else 0 end) as rate_count
from items
group by date,id;
quit;
This has not yielded the desired result and the challenge I have here is to check the transaction dates (4/14/2017 and 4/20/2017) and next business day dates (4/17/2017,4/21/2017).
Appreciate your help.

Answer 1

LAG function will do the trick here. As we can use lagged values to create the condition we want without having to use the rate>5 condition.
Here is the solution:-
Data items;
set items;
Lag_dt=LAG(Date);
Lag_id=LAG(id);
Lag_rate=LAG(rate);
if ((id=lag_id) and (code=121) and (Date>lag_dt)) then rate_count=(rate/lag_rate);
else rate_count=0;
Drop lag_dt lag_id lag_rate;
run;
Hope this helps.