我有两个数据文件sh1和sh2。

其中sh1：ID

               aa

               aa

                bb

               cc

              cc

sh2：ID          TOTAL

          aa              150

         bb               100

          cc                60

现在我想把根据sh2，将sh1变成：ID   TOTAL

                                                      aa     150

                                                      aa      150

                                                      bb       100

                                                       cc      60

                                                        cc     60

我写的语句是：n1<-length(sh1$ID);n2<-length(sh2$ID);

                   for(i in 1:n2){for(j in 1:n1) if(sh1$ID[j]==sh2$ID) sh1$TOTAL[j]<-sh2$TOTAL;j<-j+1}i<-i+1}

这个运行倒是没问题，但是效率很低。请问有没有更好的办法呢？