1、merge函数对数据框的操作 从两个数据框中选择出条件相等的行组合成一个新的数据框 df1=data.frame(name=c("aa","bb","cc"),age=c(20,29,30),sex=c("f","m","f"))df2=data.frame(name=c("dd","bb","cc"),age=c(40,35,36),sex=c("f","m","f"))mergedf=merge(df1,df2,by=...