**你需要用 week() function,把 days 分成几大组, 再求平均值.***;
data a;
input days: yymmdd10. return;
format days yymmdd10.;
cards;
19260102 0.001533742
19260104 -0.004594181
19260105 0.001538462
19260106 0.002304148
19260107 0.009578544
19260108 0.020113852
19260109 0.017485119
19260111 -0.001462523
19260112 0.015378982
19260113 -0.016227912
19260114 -0.008797654
19260115 -0.008505917
19260116 0.001118986
19260118 0.000745157
;
run;
proc print data=a;
run;
data b;
set a;
weeks=week(days);
run;
proc print data=b;
run;
proc means data=b;
class weeks;
var return;
run;