Tidyverse 按行绑定未命名向量列表的方法 - do.call(rbind,x) 等效 [英] Tidyverse approach to binding unnamed list of unnamed vectors by row - do.call(rbind,x) equivalent

问题描述

我经常发现人们以某种​​方式以未命名 未命名字符向量列表结束的问题，他们希望将它们逐行绑定到 data.frame.这是一个例子:

I often find questions where people have somehow ended up with an unnamed list of unnamed character vectors and they want to bind them row-wise into a data.frame. Here is an example:

library(magrittr)
data <- cbind(LETTERS[1:3],1:3,4:6,7:9,c(12,15,18)) %>%
  split(1:3) %>% unname
data
#[[1]]
#[1] "A"  "1"  "4"  "7"  "12"
#
#[[2]]
#[1] "B"  "2"  "5"  "8"  "15"
#
#[[3]]
#[1] "C"  "3"  "6"  "9"  "18"

一种典型的方法是使用来自基础 R 的 do.call.

One typical approach is with do.call from base R.

do.call(rbind, data) %>% as.data.frame
#  V1 V2 V3 V4 V5
#1  A  1  4  7 12
#2  B  2  5  8 15
#3  C  3  6  9 18

也许一种效率较低的方法是使用 base R 中的 Reduce.

Perhaps a less efficient approach is with Reduce from base R.

Reduce(rbind,data, init = NULL) %>% as.data.frame
#  V1 V2 V3 V4 V5
#1  A  1  4  7 12
#2  B  2  5  8 15
#3  C  3  6  9 18

但是，当我们考虑诸如 dplyr 或 data.table 等更现代的包时，可能会立即想到的一些方法不起作用，因为向量未命名或不是列表.

However, when we consider more modern packages such as dplyr or data.table, some of the approaches that might immediately come to mind don't work because the vectors are unnamed or aren't a list.

library(dplyr)
bind_rows(data)
#Error: Argument 1 must have names

library(data.table)
rbindlist(data)
#Error in rbindlist(data) : 
#  Item 1 of input is not a data.frame, data.table or list

一种方法可能是在向量上set_names.

One approach might be to set_names on the vectors.

library(purrr)
map_df(data, ~set_names(.x, seq_along(.x)))
# A tibble: 3 x 5
#  `1`   `2`   `3`   `4`   `5`  
#  <chr> <chr> <chr> <chr> <chr>
#1 A     1     4     7     12   
#2 B     2     5     8     15   
#3 C     3     6     9     18  

但是，这似乎比需要的步骤更多.

However, this seems like more steps than it needs to be.

因此，我的问题是什么是有效的 tidyverse 或 data.table 方法来绑定 unnamed 列表 unnamed 字符向量到 data.frame 行吗?

Therefore, my question is what is an efficient tidyverse or data.table approach to binding an unnamed list of unnamed character vectors into a data.frame row-wise?

推荐答案

不完全确定效率，但使用 purrr 和 tibble 的紧凑选项可能是:

Not entirely sure about efficiency, but a compact option using purrr and tibble could be:

map_dfc(purrr::transpose(data), ~ unlist(tibble(.)))

  V1    V2    V3    V4    V5   
  <chr> <chr> <chr> <chr> <chr>
1 A     1     4     7     12   
2 B     2     5     8     15   
3 C     3     6     9     18  

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