摘要: Say I have a data.frame:df <- data.frame(A=c(10,20,30),B=c(11,22,33), C=c(111,222,333)) A B C1 10 11 1112 20 22 2223 30 33 333If I select two (or more阅读全文
posted @ 2017-12-16 07:13 emanlee 阅读(44) 评论(0) 编辑