在R中拆分与合并数据

数据的拆分与合并可以使用reshape2这个包，主要使用两个命令：melt/cast（dcast返回数据框）

一、准备数据

> A <- c("A","B","C","D")
> B <- c(1,2,3,4)
> C <- c("Apple","Orange","Pear","Banana")
> D <- c("Sun","Moon","Earth","Star")
> data <- data.frame(A,B,C,D)
> data
  A B      C     D
1 A 1  Apple   Sun
2 B 2 Orange  Moon
3 C 3   Pear Earth
4 D 4 Banana  Star

二、数据拆分

> library(reshape2)

> data2 <- melt(data,id=c("A","B"))
> data2
  A B variable  value
1 A 1        C  Apple
2 B 2        C Orange
3 C 3        C   Pear
4 D 4        C Banana
5 A 1        D    Sun
6 B 2        D   Moon
7 C 3        D  Earth
8 D 4        D   Star

三、数据合并

> data3 <- dcast(data2,A+B~variable)
> data3
  A B      C     D
1 A 1  Apple   Sun
2 B 2 Orange  Moon
3 C 3   Pear Earth
4 D 4 Banana  Star