Documentation Example 3 for PROC PSMATCH

/****************************************************************/
/*          S A S   S A M P L E   L I B R A R Y                 */
/*                                                              */
/*    NAME: PSMCHEX3                                            */
/*   TITLE: Documentation Example 3 for PROC PSMATCH            */
/* PRODUCT: STAT                                                */
/*  SYSTEM: ALL                                                 */
/*    KEYS: Propensity score matching                           */
/*   PROCS: PSMATCH                                             */
/*    DATA:                                                     */
/*                                                              */
/* SUPPORT: Yang Yuan             UPDATE: Oct 17, 2016          */
/*     REF: PROC PSMATCH, EXAMPLE 3                             */
/*    MISC:                                                     */
/****************************************************************/

data drug1;
   do jorder=1 to 490;
      if (ranuni(99) < .55) then Gender='Male  ';
      else                       Gender='Female';

      Age= 30 + 20*ranuni(99) + 3*rannor(9);
      if (Age < 25) then  Age= 20 - (Age-25)/2;
      Age= int(Age);

      BMI= 20 + 6*ranuni(99) + 0.02*Age + rannor(9);
      if (BMI < 18) then BMI= 18 - (BMI-18)/4;
      BMI= int(BMI*100) / 100;

      pscore= 4. - 0.35*Age + 0.35*BMI + 0.01*rannor(99);
      if (Gender='Female') then pscore= pscore - 0.2;

      id1= ranuni(99);
      output;
   end;
run;

proc sort data=drug1 out=drug2;
   by pscore;
run;
proc rank data=drug2 out=drug3 descending;
   var pscore;
   ranks porder;
run;

data drug4;
   set drug3;
   if (porder < 100) then do;
      if (ranuni(99) < .45) then Drug= 'Drug_X';
      else                       Drug= 'Drug_A';
   end;
   else if (porder < 300) then do;
      if (ranuni(99) < .30) then Drug= 'Drug_X';
      else                       Drug= 'Drug_A';
   end;
   else if (porder < 450) then do;
      if (ranuni(99) < .15) then Drug= 'Drug_X';
      else                       Drug= 'Drug_A';
   end;
   else                          Drug= 'Drug_A';
run;

data drug5;
   set drug4;
   if (porder > 4);
run;

proc sort data=drug5;
   by id1;
run;

data drug5;
   set drug5;
   PatientID= _n_;
run;

proc sort data=drug5 out=drugs (keep=PatientID Drug Gender Age BMI);
   by jorder;
run;


ods graphics on;
proc psmatch data=drugs region=treated(extend(distance=ps mult=one)=0.025);
   class Drug Gender;
   psmodel Drug(Treated='Drug_X')= Gender Age BMI;
   match distance=ps method=varratio(kmin=1 kmax=4) exact=(Gender) caliper=.
         nmatchmost=5;
   assess ps var=(Gender Age BMI)
          / stddev=pooled(allobs=no) plots(orient=vertical nodetails);
   id BMI;
   output out(obs=match)=OutEx3 matchid=_MatchID;
run;

proc sort data=OutEx3 out=OutEx3a;
   by _MatchID;
run;

proc print data=OutEx3a(obs=10);
   var PatientID Drug Gender Age BMI _PS_ _MATCHWGT_ _MatchID;
run;