sas - Create function of two variables with do loop -

i calculate variables ar_1 ar_99 based upon formula

ar_(i) = 0.5*(adm_(i) + adm_(j))  

where j=i+1 (adm_1 adm_100 exist in dataset). using following loop error sas not recognise variable j.

%macro do_loop;  data testdo; set popn99;  %do = 1 %to 99;   &j.=&i.+1;   ar_&i. = 0.5 * (adm_&i. + adm_&j.); %end;  run;  %mend do_loop;  %do_loop; 

try:

%macro do_loop;  data testdo; set popn99;  %do = 1 %to 99;   ar_&i. = 0.5 * (adm_&i. + adm_%eval(&i.+1) ); %end;  run;  %mend do_loop;  %do_loop; 

remember sas macro code writes text only. following assignment, should have resolved (which wouldn't "j" macro variable didn't exist), have assigned value "column".

  &j.=&i.+1; 

that not have been re-used macro variable in subsequent step.

to generalise - sas macro language writes sas programs (base code) subsequently execute produce results..