Mixed-Level Design with Collapsing Factors

/****************************************************************/
/*          S A S   S A M P L E   L I B R A R Y                 */
/*                                                              */
/*    NAME: FACTEX6C                                            */
/*   TITLE: Mixed-Level Design with Collapsing Factors          */
/* 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:                                                     */
/*                                                              */
/****************************************************************/

proc factex;
   factors x1-x4 / nlev = 3;
   size design=27;
   model r=4;
   output out=MixedLevel x1 nvals=(-1 1 -1)
                         x2 nvals=(-1 1 -1);
run;
proc print data=MixedLevel;
run;