result comparing to previous month

[J_J_J]

Hi everyone!

I have data like this:

data have;
ID='A';  year=2020;	month=11; rate=50; output;
ID='A';  year=2020;	month=12; rate=20; output;
ID='A';  year=2021;	month=1; rate=70; output;
ID='A';  year=2021;	month=2; rate=50; output;
ID='A';  year=2021;	month=3; rate=50; output;
ID='A';  year=2021;	month=4; rate=45; output;
ID='A';  year=2021;	month=5; rate=40; output;
ID='A';  year=2021;	month=6; rate=35; output;
ID='A';  year=2021;	month=7; rate=30; output;
ID='A';  year=2021;	month=8; rate=25; output;
ID='A';  year=2021;	month=9; rate=25; output;
ID='A';  year=2021;	month=10; rate=25; output;
ID='A';  year=2021;	month=11; rate=20; output;
ID='A';  year=2021;	month=12; rate=15; output;
ID='B';  year=2020;	month=11; rate=65; output;
ID='B';  year=2020;	month=12; rate=35; output;
ID='B';  year=2021;	month=1; rate=85; output;
ID='B';  year=2021;	month=2; rate=65; output;
ID='B';  year=2021;	month=3; rate=65; output;
ID='B';  year=2021;	month=4; rate=60; output;
ID='B';  year=2021;	month=5; rate=55; output;
ID='B';  year=2021;	month=6; rate=50; output;
ID='B';  year=2021;	month=7; rate=45; output;
ID='B';  year=2021;	month=8; rate=40; output;
ID='B';  year=2021;	month=9; rate=40; output;
ID='B';  year=2021;	month=10; rate=40; output;
ID='B';  year=2021;	month=11; rate=35; output;
ID='B';  year=2021;	month=12; rate=30; output;

;run;

and I'd like to find result to each row comparing previous month rate with next month rate:

id	year	month	rate	result
A	2020	11	50
A	2020	12	20	green
A	2021	1	70	red
A	2021	2	50	green
A	2021	3	50	yellow
A	2021	4	45	green
A	2021	5	40	green
A	2021	6	35	green
A	2021	7	30	green
A	2021	8	25	green
A	2021	9	25	yellow
A	2021	10	25	yellow
A	2021	11	20	green
A	2021	12	15	green
B	2020	11	65
B	2020	12	35	green
B	2021	1	85	red
B	2021	2	65	green
B	2021	3	65	yellow
B	2021	4	60	green
B	2021	5	55	green
B	2021	6	50	green
B	2021	7	45	green
B	2021	8	40	green
B	2021	9	40	yellow
B	2021	10	40	yellow
B	2021	11	35	green
B	2021	12	30	green

If next month rate is less than previous one then result is 'green', if gather then 'red' and if it doesn't change then it's 'yellow'

Do you have any good ideas, how to do it without creating tables for each pair of months?

Have a nice day

[Kurt_Bremser · Accepted solution]

Kudos for supplying usable example data.

Try this:

data want;
set have;
by id;
length result $6;
l_rate = lag(rate);
if not first.id
then do;
  if l_rate > rate then result = "Green";
  else if l_rate < rate then Result = "Red";
  else result = "Yellow";
end;
drop l_rate;
run;

[J_J_J]

Kurt, thank you so much for good solution!