Hi All,
Below is the program i am running on my SAS Eg. In the last data step i am facing a problem.
Why the lag function is not assigning the value to sum_ncbal whenever the condition is true?
data in;
input seg $ period ncbal;
datalines;
A 1 10
A 2 20
A 3 30
A 4 40
A 5 50
A 6 60
A 7 70
A 8 80
A 9 90
A 10 100
A 11 110
A 12 120
B 1 1
B 2 2
B 3 3
B 4 4
B 5 5
B 6 6
B 7 7
B 8 8
B 9 9
B 10 10
B 11 11
B 12 12
;
run;
proc sort data=in ;
by seg descending period;
run;
Data in1;
set in;
by seg;
if first.seg then count=0;
count+1;
if count = 2 then sum_ncbal= lag(ncbal);
run;
LAG is trickier than it looks. It seems that you want the value of NCBAL from the previous observation, but that's not what LAG does. It actually retrieves the value from the last time that the LAG function executed. To get the value from the previous observation, make sure that LAG executes every time. For example:
Data in1;
set in;
by seg;
tempvar = lag(ncbal);
drop tempvar;
if first.seg then count=0;
count+1;
if count = 2 then sum_ncbal= tempvar;
run;
The lag() functions only fill their queue when called. Calling them conditionally usually results in arbitrary return values.
Do this:
data in1;
set in;
by seg;
if first.seg
then count = 1;
else count + 1;
sum_ncbal = lag(ncbal);
if count = 2 then sum_ncbal = .;
run;
if you already have values in sum_ncbal that need to be preserved, do this
data in1;
set in;
by seg;
if first.seg
then count = 1;
else count + 1;
lag_ncbal = lag(ncbal);
if count = 2 then sum_ncbal = lag_ncbal;
drop lag_ncbal;
run;
Are you ready for the spotlight? We're accepting content ideas for SAS Innovate 2025 to be held May 6-9 in Orlando, FL. The call is open until September 25. Read more here about why you should contribute and what is in it for you!
Learn how use the CAT functions in SAS to join values from multiple variables into a single value.
Find more tutorials on the SAS Users YouTube channel.