/* Match merge to create a sum of squares   */
data a;
input x id @@;
datalines;
13 1 14 2 12 1 19 2 23 1 42 3 19 3 27 1 28 3 28 2 19 3
;
proc sort data=a; by id;
proc means data=a noprint; by id;
output out=outa;
run;
/* The BY statement creates alot of junk that needs cleaned up        */
data outb; set outa; if _stat_='MEAN'; drop _stat_ _type_ _freq_ x; xbar=x; run;
/* One more sort just to be safe     */
proc sort data=outb; by id;
/* Accumulate the sum of squares to create a pooled SS          */
data c; merge a outb; by id; devsq=(x-xbar)*(x-xbar); ssq+devsq; *ssq may need work;
proc print data=c; run;

/* Same steps as above, but we will use some data step options     */
/* Note that I can't drop _stat_ or the WHERE statement won't work */
/* And I keep x, even though I renamed it xbar                     */
data a;
input x id @@;
datalines;
13 1 14 2 12 1 19 2 23 1 42 3 19 3 27 1 28 3 28 2 19 3
;
proc sort data=a; by id;
proc means data=a noprint; by id;
output out=outa (where=(_stat_='MEAN') rename=(x=xbar) keep=id x _stat_) ;
run;

proc print data=outa; run;