topic Re: Running sum in Array statement in SAS Procedures

Running sum in Array statement

apat86 — Sun, 28 Nov 2010 21:49:10 GMT

Hello,

I have 365 variables each for a day in particular year (i.e. Jan01--Dec31). I need to find sum of 60 days only. I used array statement to find sum, but i need to mansion all 60 variables. Can I use "Total=Sum (of var {i+1}--var{i+60})" ? It is not working with my program.

Any suggestions highly appreciated.

Thank you..

Re: Running sum in Array statement

ArtC — Mon, 29 Nov 2010 00:46:09 GMT

While you can't use array values as list elements, you can do what you want by using a stack. The stack avoids a loop that passes through the array multiple times.

The following silly program creates the first sum and then for each successive sum removes the oldest value and adds the newest (FIFO stack).
[pre]
data days(keep=day:);
array days {366} day1-day366;
do i = 1 to 365;
days{i} = 1;
end;
output;
run;

data sums(keep=period sum);
set days;
retain sum .;
array days {366} day1-day366;
period=1;
sum = sum(of day1-day60);
output;
do period = 2 to 306;
sum = sum(of sum, -days{period-1},days{period+60});
output sums;
end;
run;[/pre]

Re: Running sum in Array statement

Ksharp — Mon, 29 Nov 2010 01:32:43 GMT

Hi.
Not sure what variables you need to sum.
But SUM function supports not only list input but also colon input.
For example you need to sum January and February.
[pre]
sum(of jan: feb:)
[/pre]

Ksharp