topic Re: index value in array in SAS Programming

index value in array

SAS_inquisitive — Mon, 19 Jun 2017 12:07:35 GMT

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;

Re: index value in array

PeterClemmensen — Mon, 19 Jun 2017 12:25:38 GMT

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;

Re: index value in array

Kurt_Bremser — Mon, 19 Jun 2017 12:27:20 GMT

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.

Re: index value in array

art297 — Mon, 19 Jun 2017 12:34:17 GMT

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

Re: index value in array

SAS_inquisitive — Mon, 19 Jun 2017 13:11:20 GMT

@Kurt_Bremser What are numeric values 7 and 2?

Re: index value in array

Kurt_Bremser — Mon, 19 Jun 2017 13:24:50 GMT

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?

Re: index value in array

SAS_inquisitive — Mon, 19 Jun 2017 13:35:22 GMT

Thank you all for the explanation.