这段程序是什么意思啊？

shiyiming

proc expand data=work.drawing_summary out=work.drawing_averages method=none;
by mach;
id xjoin;
convert lb=lb_movavg2/transform=(reverse movave 2 reverse);
convert lb_h=lbhr_movavg2/transform=(reverse movave 2 reverse);
convert act_=act_movavg2/transform=(reverse movave 2 reverse);
convert st=st_movavg2/transform=(reverse movave 2 reverse);
convert cv_=cv_movavg2/transform=(reverse movave 2 reverse);
run;

有没有什么错误呀？ <!-- s:oops: --><img src="{SMILIES_PATH}/icon_redface.gif" alt=":oops:" title="Embarassed" /><!-- s:oops: -->