R reshape2 dcast：转换数据

Question

如何将数据X转换为Y

X = data.frame(
  ID = c(1,1,1,2,2),
  NAME = c("MIKE","MIKE","MIKE","LUCY","LUCY"),
  SEX = c("MALE","MALE","MALE","FEMALE","FEMALE"),
  TEST = c(1,2,3,1,2),
  SCORE = c(70,80,90,65,75)
)

Y = data.frame(
  ID = c(1,2),
  NAME = c("MIKE","LUCY"),
  SEX = c("MALE","FEMALE"),
  TEST_1 =c(70,65),
  TEST_2 =c(80,75),
  TEST_3 =c(90,NA)
)

假设一个ID列的所有其他列都是一致的，比如Mike只能是ID为1的男性，我们怎么做呢？

Answer 1

根据文档(？reshape2::dcast)，dcast()允许在公式中使用...:

“……”表示公式中未使用的所有其他变量。..

对于reshape2和data.table包都是这样，它们都支持dcast（）。

reshape2::dcast(X, ... ~ TEST, value.var = "SCORE")
#  ID NAME    SEX  1  2  3
#1  1 MIKE   MALE 70 80 90
#2  2 LUCY FEMALE 65 75 NA

但是，如果OP坚持列名应该是test_1、test_2等，则在重新成形之前需要修改test列。这里使用data.table:

library(data.table)
dcast(setDT(X)[, TEST := paste0("TEST_", TEST)], ... ~ TEST, value.var = "SCORE")
#   ID NAME    SEX TEST_1 TEST_2 TEST_3
#1:  1 MIKE   MALE     70     80     90
#2:  2 LUCY FEMALE     65     75     NA

这与作为data.framey给出的预期答案一致。