Matching with Replacement - support region does not exist

[lioradam]

Hello all,

I wrote the code for Matching with Replacement as in the following  Example 98.6 from the SAS User's Guide:

proc psmatch data=School region=allobs(psmin=0.05);

   class Music Gender;

   psmodel Music(Treated='Yes')= Gender Absence;

   match method=replace(k=1) distance=ps exact=Gender caliper=.

         nmatchmost=6;

   assess ps var=(Gender Absence);

   output out(obs=match)=outex6 matchid=_MatchID;

run;

and I get the error message:

ERROR: The support region does not exist.

I try to change the region to psmin=0.01 or psmin=0.001 but I keep getting the same error message.

Could anyone please advise what I'm doing wrong?

Thanks.

Lior

[ghosh]

It ran fine when I created the school dataset using the code referenced in the example.  see here

https://documentation.sas.com/doc/en/pgmsascdc/9.4_3.4/statug/statug_code_psmchex4.htm

[lioradam]

Hi,

In my data, it didn't work...

I thought that if I reduce the "psmin"  to be close to zero, I should avoid this error message, but it didn't work...

when I use a different type of matching: "Greedy Nearest Neighbor Matching" it works fine. so I believe there is no problem with my data, but maybe I don't understand how code works.

Thanks,

Lior

[ghosh]

I ran your code after creating the school dataset from the example and did not get any errors

data School;
   Music= 'Yes';
   do j=1 to 60;
      if (ranuni(1312) > 0.4) then Gender='Female';
      else                         Gender='Male';

      Absence = ranexp(99);
      if (Absence < 0.5) then GPA= 4 + rannor(99)/3.5;
      else                    GPA= 4 - abs(rannor(99)/3.5);

      if (Gender='Female') then GPA= GPA + 0.02;

      id1= ranuni(99);
      id2= ranuni(99);
      output;
   end;

   Music= 'No';
   do j=1 to 100;

      Absence= ranexp(99);
      if (ranuni(99) > 0.45) then Gender='Female';
      else                        Gender='Male';
      if (Absence < 0.5) then GPA= 4 + rannor(99)/4.2;
      else                    GPA= 4 - abs(rannor(99)/4.2);

      id1= ranuni(99);
      id2= ranuni(99);
      output;
   end;

   do j=1 to 40;
      Absence= 2 + ranexp(99);
      if (ranuni(99) > 0.5) then Gender='Female';
      else                       Gender='Male';

      GPA= 3.4 - abs(rannor(99)/4.2);

      id1= ranuni(99);
      id2= ranuni(99);
      output;
   end;
run;

proc sort data=school;
   by id1;
run;

data school;
   set school;
   StudentID= _n_;
   Absence= int(Absence*100+0.5) / 100;
   GPA= int(GPA*100+0.5) / 100;
run;

proc sort data=school;
   by id2;
run;

proc print data=School(obs=10);
   var StudentID Music Gender Absence;
run;

proc psmatch data=School region=allobs(psmin=0.05);
   class Music Gender;
   psmodel Music(Treated='Yes')= Gender Absence;
   match method=replace(k=1) distance=ps exact=Gender caliper=.
         nmatchmost=6;
   assess ps var=(Gender Absence);
   output out(obs=match)=outex6 matchid=_MatchID;
run;