This is the code for the moving SUM:   /* Create monthly sales data from January 2008 to December 2010 */ data test; do mo_period = '01jan2008'd to '31dec2010'd; sales = round(ranuni(1234567) * 1000, .01); mo_period = intnx('month', mo_period, 0, 'END'); output; end; format mo_period monyy7. sales comma10.2; run; /* Specify the number of periods in the rolling sum and average */ %let roll_num = 12; data new; set test; /* Create array with specific number of elements. */ /* Passing _temporary_ arrays as arguments to functions is not supported */ /* until SAS 9.2. */ /* If the array is a _TEMPORARY_ array, the elements are automatically retained */ array summed[&roll_num] _temporary_; /* Alternatively, a non-temporary array can be used but it must be retained: */ /* array summed[&roll_num];*/ /* retain summed;*/ /* E represents the element of the array to assign a sales value. */ /* Increment it by one unless it is equal to &roll_num, at which point */ /* start over and assign it a value of 1. This causes the oldest period to */ /* be replaced by the newest period once &roll_num periods have been read. */ if E = &roll_num then E = 1; else E + 1; /* Assign value to proper element of the array */ summed[E] = sales; /* Start summing once &roll_num values have been read from the data set */ if _N_ >= &roll_num then do; roll_sum = sum(of summed[*]); roll_avg = mean(of summed[*]); end; format roll_sum roll_avg comma10.2; run; ... View more