Here is one.

data _null_;
   call symputx('lastobs',lastobs);
   stop;
   set sashelp.class nobs=lastobs;
run;

%put >>>&lastobs<<<;

bob的回复应该和lz的要求不太一致，改了下

data t;
   set sashelp.class nobs=lastobs;
   if _N_ EQ lastobs then call symputx('lastage',Age);
run;

%put >>>&lastage<<<;

另外问下bob兄，stop好像加不加都行，有什么具体的作用吗？谢谢！

Stop statement will stop SAS internal loops.

The point here is to access last and only last obs.

data _null_;
   point=lastobs;
   set sashelp.class nobs=lastobs point=point;
   call symputx('lastage',Age);
   stop;
run;

%put >>>&lastage<<<;

Stop statement will stop SAS internal loops.

The point here is to access last and only last obs.

data _null_;
   point=lastobs;
   set sashelp.class nobs=lastobs point=point;
   call symputx('lastage',Age);
   stop;
run;

%put >>>&lastage<<<;

I thought the original request is to pass # of obs to a macro variable.

The nobs of a data set is available at compiling time.