/*--------------------------------------------------------------------------------
   Macro BOXTID

   Author      : Carina Ortseifen (carina.ortseifen@urz.uni-heidelberg.de)
    
   Version     : 1.0 (01.04.98)

   Subject     : Boxed-Tidwell transformation of variable var with power p

   Result      : var**p    if p != 0
                 log(var)  otherwise

   Hints       : use this macro inside a data step and an assignment

   Example     : * Sample data step shows 3**2=9 in log window;
                 data _null_;
                      x=%boxtid(3,2);
                      put x;
                 run;
--------------------------------------------------------------------------------*/
%macro boxtid(var,p);

       %if &p=0 %then log(&var);
       %else &var**(&p);

%mend;