topic Re: do loop in SAS Programming

do loop

sanyam13 — Tue, 26 Jun 2018 13:52:28 GMT

data test;
do year = 1 to 5;
do month = 1 to 12;
x+1;
output;
end;
end;
run;

can somebody explain how this nested loop works , how I m getting 60 observations in output ?

Re: do loop

kiranv_ — Tue, 26 Jun 2018 14:00:22 GMT

see the below link, it clearly explains about nesting loops.

https://onlinecourses.science.psu.edu/stat481/node/42/

Re: do loop

RW9 — Tue, 26 Jun 2018 14:12:21 GMT

Break it down:

do year = 1 to 5; < - do this code 5 times
do month = 1 to 12;
x+1;
output;
end;
end;

For each of those five times:

do month = 1 to 12; <- do this code 12 times

x+1;
output;

Thus you are running 12 times (inner loop) for each of the 5 times (outer loop) = 60 iterations.

Re: do loop

novinosrin — Tue, 26 Jun 2018 14:24:25 GMT

@sanyam13 A quick way to grasp the way my professor taught me a loop construct in any programming language

1. inner most look executes in full and followed by one by one to reverse top order

2. total number of loops processed = stopvalue1*stopvalue2*stopvalueN= 5*12=60 in your case

Re: do loop

FreelanceReinh — Tue, 26 Jun 2018 15:03:17 GMT

@novinosrin wrote:

2. total number of loops processed = stopvalue1*stopvalue2*stopvalueN= 5*12=60 in your case

@sanyam13: It goes without saying that "stop value" in the above calculation does not always equal the value following the TO keyword (such as 10 in do i=1 to 10), but can differ from that value in many ways depending on start value (do i=0 to 10), increment (do i=1 to 10 by 2), WHILE/UNTIL conditions, the code performed in the loop (e.g. LEAVE statement), etc.