A Factorial Design with Center Points

/****************************************************************/
/*          S A S   S A M P L E   L I B R A R Y                 */
/*                                                              */
/*    NAME: FACTEX9                                             */
/*   TITLE: A Factorial Design with Center Points               */
/* PRODUCT: QC                                                  */
/*  SYSTEM: ALL                                                 */
/*    KEYS: Design of Experiments, Factorial Designs,           */
/*   PROCS: FACTEX                                              */
/*    DATA:                                                     */
/*                                                              */
/*     REF: SAS/QC Software:  Usage and Reference, Version 6,   */
/*          First Edition, Volume 1 and Volume 2                */
/*    MISC:                                                     */
/*                                                              */
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proc factex;
   factors Current Voltage Time;
   output out=Factorial
          Current nvals=(12  28)
          Voltage nvals=(100 200)
          Time    nvals=(50  60);
run;

data Center(drop=i);
   do i = 1 to 4;
      Current = 20;
      Voltage = 150;
      Time    = 55;
      output;
   end;
data CPDesign;
   set Factorial Center;
run;
proc print data=CPDesign;
run;