/*****************************************************************************************************************

SAS file name: array_lag
File location: 
_________________________________________________________________________________________________________________

Purpose: To demonstrate how to store lagged values in temporary arrays in SAS
Author: Peter Clemmensen
Creation Date: 01/05/2019

This program supports the example page "Use Arrays to Store Lagged Values in SAS" on SASnrd.com

*****************************************************************************************************************/

/* Example data */
data have;
input id var @@;
datalines;
1 1 1 2 1 3 1 4 1 5
2 1 2 . 2 3 2 . 2 5
3 1 3 2 3 4 3 . 3 5
;

/* Store lagged values in a temporary array */
data want;
    array lag[0:2] _temporary_;            /* 1 */
    call missing(of lag[*], obs);          /* 2 */
    do obs=1 by 1 until (last.id);         /* 3 */
        set have;
        by id;
        lag[mod(obs, 3)]=var;              /* 4 */
        count=n(of lag[*]);                /* 5 */
        avg=mean(of lag[*]);

        temp = catq('d', '|', of lag[*]);  /* 6 */
        put temp=;

        output;
    end;
run;