程序如下：data ex1;
input price;
time=intnx('month','01jan2005'd,_n_-2);
format time monyy.;
cards;
3.41
3.45
3.42
3.44
3.46
3.48
3.49
;
proc print data=ex1;
run;

结果：
                                                 Obs    price    time

                                                  1      3.41    DEC04
                                                  2      3.45    JAN05
                                                  3      3.42    FEB05
                                                  4      3.44    MAR05
                                                  5      3.46    APR05
                                                  6      3.48    MAY05
                                                  7      3.49    JUN05
不是该一直向前吗？如果我要以jan2005为参照，向以前以一个月为间隔得出时间该用什么函数？