Question

我有一个data.frame，我需要向其中添加行，但是要添加的行数（及其内容）由data.frame的现有行确定。我还想最后列出一列，列出每个重复组的行。这是示例数据：

> A <- data.frame(veh = c("MINIVAN","HEAVY TRUCK"),age = c(2.5,3.5),rows_to_add = c(2,3))
> A
          veh age rows_to_add
1     MINIVAN 2.5           2
2 HEAVY TRUCK 3.5           3

和所需的输出：

> B <- rbind(do.call("rbind",replicate(n=unique(A[1,"rows_to_add"])+1,A[1,],simplify = FALSE)),
+ do.call("rbind",replicate(n=unique(A[2,"rows_to_add"])+1,A[2,],simplify = FALSE)))
> B <- cbind(B,enum = c(0:2,0:3))
> B
           veh age rows_to_add enum
1      MINIVAN 2.5           2    0
2      MINIVAN 2.5           2    1
3      MINIVAN 2.5           2    2
24 HEAVY TRUCK 3.5           3    0
21 HEAVY TRUCK 3.5           3    1
22 HEAVY TRUCK 3.5           3    2
23 HEAVY TRUCK 3.5           3    3

很显然，我在这里用来生成输出的代码是混乱的，不可伸缩的，并且可能效率低下。我正在寻找一种通用的解决方案，该解决方案允许我以合理的速度使用较大的data.frame来做到这一点，并避免出现循环（尝试加快加载循环的代码是此问题的推动力）。

This question处理的问题较弱，其中添加的行数不随数据本身的行而变化，并且要插入的行可以包含NA，但我没有办法在那儿概括答案。

一般来说我如何才能获得所需的输出？

Answer 1

一种base R方法

out <- A[rep(seq_len(nrow(A)), A$rows_to_add + 1), ]
out
#            veh age rows_to_add
#1       MINIVAN 2.5           2
#1.1     MINIVAN 2.5           2
#1.2     MINIVAN 2.5           2
#2   HEAVY TRUCK 3.5           3
#2.1 HEAVY TRUCK 3.5           3
#2.2 HEAVY TRUCK 3.5           3
#2.3 HEAVY TRUCK 3.5           3

按照@thelatemail在评论中建议的方式添加新列

out$enum <- sequence(unique(A$rows_to_add) + 1) - 1
#out <- transform(out, enum = ave(age, rows_to_add, FUN = seq_along) - 1) # my slower attempt
#            veh age rows_to_add enum
#1       MINIVAN 2.5           2    0
#1.1     MINIVAN 2.5           2    1
#1.2     MINIVAN 2.5           2    2
#2   HEAVY TRUCK 3.5           3    0
#2.1 HEAVY TRUCK 3.5           3    1
#2.2 HEAVY TRUCK 3.5           3    2
#2.3 HEAVY TRUCK 3.5           3    3

使用data.table

可能更快

library(data.table)
setDT(A)
out <- A[rep(seq_len(dim(A)[1]), A[, rows_to_add] + 1)
         ][, enum := sequence(unique(rows_to_add) + 1) - 1]
out

Answer 2

您需要uncount中的tidyr-

library(dplyr)
library(tidyr)

A %>% 
  uncount(weights = rows_to_add + 1, .id = "enum") %>%
  mutate(
    enum = enum - 1
  )

          veh age rows_to_add enum
1     MINIVAN 2.5           2    0
2     MINIVAN 2.5           2    1
3     MINIVAN 2.5           2    2
4 HEAVY TRUCK 3.5           3    0
5 HEAVY TRUCK 3.5           3    1
6 HEAVY TRUCK 3.5           3    2
7 HEAVY TRUCK 3.5           3    3

对于每个数据框行，添加x行，其中从该行获得x

2 个答案: