r - %>% 运算符中的 dplyr 重复

Question

我正在尝试将 rep 与 dplyr 一起使用，但我不完全理解为什么我不能让它工作。

我的数据如下所示。我想要的是通过 n 为每个 id 简单地重复 dayweek。

head(dt4)

   id  dayweek n
1  1   Friday 3
2  1   Monday 3
3  1 Saturday 3
4  1   Sunday 3
5  1 Thursday 3
6  1  Tuesday 3

我要做的是在 dplyr 流程中这样做

cbind(rep(dt4$id, dt4$n), rep(as.character(dt4$dayweek), dt4$n) ) 

这给了

    [,1] [,2]    
[1,] "1"  "Friday"
[2,] "1"  "Friday"
[3,] "1"  "Friday"
[4,] "1"  "Monday"
[5,] "1"  "Monday"
[6,] "1"  "Monday"

我不明白为什么这段代码不起作用

dt4 %>% 
  group_by(id) %>% 
  summarise(rep(dayweek, n))

Error: expecting a single value

有人可以帮我解决这个问题吗？

数据

dt4 = structure(list(id = c(1L, 1L, 1L, 1L, 1L, 1L, 1L, 2L, 2L, 2L, 
2L, 2L, 2L, 2L, 3L, 3L, 3L, 3L, 3L, 3L, 3L), dayweek = structure(c(1L, 
2L, 3L, 4L, 5L, 6L, 7L, 1L, 2L, 3L, 4L, 5L, 6L, 7L, 1L, 2L, 3L, 
4L, 5L, 6L, 7L), .Label = c("Friday", "Monday", "Saturday", "Sunday", 
"Thursday", "Tuesday", "Wedesnday"), class = "factor"), n = c(3, 
3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3)), class =     "data.frame", .Names = c("id", 
"dayweek", "n"), row.names = c(NA, -21L))

Answer 1

data.table可以作为这种类型的操作操作的有用替代方案 - 我发现这更容易阅读:

library("data.table")
dt4 <- as.data.table(dt4)
head(dt4[, rep(dayweek, n), by=id], 10)

给予:

    id       V1
 1:  1   Friday
 2:  1   Friday
 3:  1   Friday
 4:  1   Monday
 5:  1   Monday
 6:  1   Monday
 7:  1 Saturday
 8:  1 Saturday
 9:  1 Saturday
10:  1   Sunday