Hello,
Why is the value of index (i) 2 in below two programs since the loop iterates just only for once?
data have;
input x y;
cards;
1 2
;
data want;
set have;
array ar{*} x y;
do i = 1 to dim(ar)-1;
put i =;
var = ar{i+1}-ar{i};
end;
put i =;
run;
data have;
input x y;
cards;
1 2
;
data want;
set have;
array ar{*} x y;
do i = 1 to dim(ar)-1;
put i =;
var = ar{i}-ar{i};
end;
put i =;
run;
A do loop works like that:
1 - set index variable to initial value
2 - compare index variable with termination value
3 - if higher goto 7
4 - execute loop body
5 - increment index value
6 - goto 2
7 - end
So you see that the loop terminates only when the index variable exceeds the termination value.
When i increases to be > dim(ar)-1, the statements inside the loop are not executed. So i increases to be equal to 2, but i is never equal to two inside the loop. Run this program to verify
data have;
input x y;
cards;
1 2
;
data want;
set have;
array ar{*} x y;
do i = 1 to (dim(ar)-1);
put i=;
var = ar{i+1}-ar{i};
end;
run;
A do loop works like that:
1 - set index variable to initial value
2 - compare index variable with termination value
3 - if higher goto 7
4 - execute loop body
5 - increment index value
6 - goto 2
7 - end
So you see that the loop terminates only when the index variable exceeds the termination value.
@Kurt_Bremser What are numeric values 7 and 2?
These are just "line numbers" similar to those used in eg BASIC, to identify places in the code.
@SAS_inquisitive wrote:
@Kurt_Bremser What are numeric values 7 and 2?
The index of a do loop, by definition, increases until it exceeds it's "to" value. When it does exceed that value, it exits from the loop with processing the commands within the loop.
Art, CEO, AnalystFinder.com
Don't miss out on SAS Innovate - Register now for the FREE Livestream!
Can't make it to Vegas? No problem! Watch our general sessions LIVE or on-demand starting April 17th. Hear from SAS execs, best-selling author Adam Grant, Hot Ones host Sean Evans, top tech journalist Kara Swisher, AI expert Cassie Kozyrkov, and the mind-blowing dance crew iLuminate! Plus, get access to over 20 breakout sessions.
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.