规则明确下，是补到4间隔1还是其他

data time (drop=qtr);   
input id $ year qtr;
qtr_new = yyq(year, qtr);
format qtr_new yyq6.;
cards;
a        1999 1
a        1999 2
a        1999 4
b        1999 3
b        2000 1
;
run;

proc sort data=time;
by id qtr_new;
run;
   
proc expand data=time out=time_new (drop=year) to=qtr method=none ;
by id;
id qtr_new;
run;

  *The following is optional if you like

data time_new1;
set time_new;
year=year(qtr_new);
qtr=qtr(qtr_new);
run;

什么意思     间隔为1的补齐

data b(keep=id year qtr);
set a;
mdy=yyq(year,qtr);
format mdy yyq6.;
lag1=lag(mdy);
interval=intck("qtr",lag1,mdy);
if interval=2 then do;
mdy1=intnx("qtr",lag1,1);
year=year(mdy1);
qtr=qtr(mdy1);
end;
if interval=2;
run;
proc append base=a data=b force;run;
proc sort data=a;by id year;run;