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="name") 2、subset函数,从某一个数据框中选择出符合某条件的数据或是相关的列 (1)单条件查询 > selectresult=subset(df1,name=="aa") > selectresult name age sex 1 aa 20 f > df1 name age sex 1 aa 20 f 2 bb 29 m 3 cc 30 f (2)指定显示列 > selectresult=subset(df1,name=="aa",select=c(age,sex)) > selectresult age sex 1 20 f (3)多条件查询 > selectresult=subset(df1,name=="aa" & sex=="f",select=c(age,sex)) > selectresult age sex 1 20 f > df1 name age sex 1 aa 20 f 2 bb 29 m 3 cc 30 f