Question

我想将dataframe转换为m x n表。编写代码并查看原始数据的简化版本，如下所示：

set.seed(1)
dat <- data.frame(x = rep(c("A","B","C","D","E"),2),
                  y = c("R","S",rep(c("P","Q","R","S"),2)),
                  val = sample(2:20,10))

   x y val
1  A R   7
2  B S   8
3  C P  11
4  D Q  16
5  E R   5
6  A S  14
7  B P  15
8  C Q   9
9  D R  19
10 E S   2

所需结果的代码：

dat2 <- data.frame(x=c("A","B","C","D","E"),
                   P=c(NA,15,11,NA,NA),
                   Q=c(NA,NA,9,16,NA),
                   R=c(7,NA,NA,19,5),
                   S=c(14,8,NA,NA,2)
                   )

  x  P  Q  R  S
1 A NA NA  7 14
2 B 15 NA NA  8
3 C 11  9 NA NA
4 D NA 16 19 NA
5 E NA NA  5  2

因此，基本上，我想将y中的所有唯一值转换为列，并添加val中的相应值，从而得到一个5x4矩阵。

Answer 1

您可以使用dcast()中的data.table：

library(data.table)
set.seed(1)
dat <- data.frame(x = rep(c("A","B","C","D","E"),2),
                  y = c("R","S",rep(c("P","Q","R","S"),2)),
                  val = sample(2:20,10))


dcast(dat, x ~ y, value.var = "val")
  x  P  Q  R  S
1 A NA NA  7 14
2 B 15 NA NA  8
3 C 11  9 NA NA
4 D NA 16 19 NA
5 E NA NA  5  2

将数据框转换为m x n表

1 个答案: