Checking correct order of values - arrays

Question

I have a data set that looks similar to the one below. Basically, I have current prices for three different sizes of an item type. If the sizes are priced correctly (ie small<medium<large) I want to flag them with a “Y” and continue to use the current price. If they are not priced correctly, I want to flag them with a “N” and use the recommended price. I know that this is probably a time to use array programming, but my array skills are, admittedly, a bit weak. There are hundreds of locations, but only one item type. I currently have the unique locations loaded in a macro variable list.
data have;
input type location $ size $ cur_price rec_price;
cards;
x NY S 4 1
x NY M 5 2
x NY L 6 3
x LA S 5 1
x LA M 4 2
x LA L 3 3
x DC S 5 1
x DC M 5 2
x DC L 5 3
;
run;
proc sql;
select distinct location into :loc_list from have;
quit;
Any help would be greatly appreciated.
Thanks.

Answer 1

Not sure why you'd want to use an array here...proc transpose and some data step logic
can easily solve this problem. Arrays are very useful (gotta admit, I'm not entirely
comfortable with them either), but in a situation where you have that many locations,
I think transpose is better.
Does the code below accomplish your goal?
/*sorts to get ready for transpose*/
proc sort data=have;
by location;
run;
/*transpose current price*/
proc transpose data=have out=cur_tran prefix=cur_price;
by location;
id size;
var cur_price;
run;
/*transpose recommended price*/
proc transpose data=have out=rec_tran prefix=rec_price;
by location;
id size;
var rec_price;
run;
/*merge back together*/
data merged;
merge cur_tran rec_tran;
by location;
run;
/*creates flags and new field for final price*/
data want;
set merged;
if cur_priceS<cur_priceM<cur_priceL then
do;
FLAG='Y';
priceS=cur_priceS;
priceM=cur_priceM;
priceL=cur_priceL;
end;
else do;
FLAG='N';
priceS=rec_priceS;
priceM=rec_priceM;
priceL=rec_priceL;
end;
run;

Answer 2

I don't see how arrays would help here. How about just checking using dif to queue the last record's price and verify it (could also retain the last price if you prefer). Make sure the dataset's properly sorted by type location descending size, then:
data want;
set have;
by type location descending size; *S > M > L alphabetically;
retain price_check;
if not first.location and dif(cur_price) lt 0 then price_check=1;
*if dif < 0 then cur rec is smaller;
else if first.location then price_check=0; *reset it;
if last.location;
keep type location price_check;
run;
Then merge that back to your original dataset by type location, and use the other price if cur_price=1.

Answer 3

Alternatively you could do it in a single query which is almost a re-statement of your requirements.
Proc sql;
create table want as
select *
/* Basically, I have current prices for three different sizes of an item type.
If the sizes are priced correctly (ie small<medium<large) */
, case
when max ( case when size eq 'S' then cur_price end)
lt max ( case when size eq 'M' then cur_price end)
and max ( case when size eq 'M' then cur_price end)
lt max ( case when size eq 'L' then cur_price end)
/* I want to flag them with a “Y” and continue to use the current price */
then 'Y'
/* If they are not priced correctly,
I want to flag them with a “N” and use the recommended price. */
else 'N'
end as Cur_Price_Sizes_Correct
, case
when calculate Cur_Price_Correct eq 'Y'
then cur_price
else rec_price
end as Price
From have
Group by Type
, Location
;
Quit;