将列表列直接取消嵌套到多列中 [英] Unnest a list column directly into several columns

问题描述

我可以将列表列直接取消嵌套到 n 列中吗?

可以假设列表是规则的，所有元素的长度相等.

如果我有一个字符向量而不是列表列，我可以tidyr::separate.我可以tidyr::unnest，但是我们需要另一个辅助变量来tidyr::spread.我错过了一个明显的方法吗?

示例数据:

图书馆(tibble)df1 <- 数据帧(gr = c('a', 'b', 'c'),值 = 列表(1:2, 3:4, 5:6))

<块引用>

# tibble: 3 x 2gr值<chr><列表>1 a<int [2]>2 b<int [2]>3 c<int [2]>

目标:

df2 <- data_frame(gr = c('a', 'b', 'c'),V1 = c(1, 3, 5),V2 = c(2, 4, 6))

<块引用>

# tibble: 3 x 3格 V1 V2<chr><dbl><dbl>1 1. 2.2 b 3. 4.3 c 5. 6.

当前方法:

unnest(df1) %>%group_by(gr) %>%变异(r = paste0('V'，row_number()))％>％传播(r，值)

解决方案

使用 tidyr 1.0.0 你可以做到:

library(tidyr)df1 <- 小标题(gr = c('a', 'b', 'c'),值 = 列表(1:2, 3:4, 5:6))unnest_wider(df1，值)#>新名称:#>* `` ->...1#>* `` ->...2#>新名称:#>* `` ->...1#>* `` ->...2#>新名称:#>* `` ->...1#>* `` ->...2#># 小费:3 x 3#>克 ...1 ...2#><chr><int><int>#>1 1 2#>2 b 3 4#>3 c 5 6

^{由 reprex 包 (v0.3.0) 于 2019 年 9 月 14 日创建}

这里的输出很冗长，因为水平未嵌套的元素(向量元素)没有命名，unnest_wider 不想默默猜测.

我们可以预先命名它们以避免它:

df1 %>%dplyr::mutate(values = purrr::map(values, setNames, c(V1",V2"))) %>%unnest_wider(值)#># 小费:3 x 3#>格 V1 V2#><chr><int><int>#>1 1 2#>2 b 3 4#>3 c 5 6

或者只是使用 suppressMessages() 或 purrr::quietly()

Can I unnest a list column directly into n columns?

The list can be assumed to regular, with all elements being of equal length.

If instead of a list column I would have a character vector, I could tidyr::separate. I can tidyr::unnest, but we need another helper variable to be able to tidyr::spread. Am I missing an obvious method?

Example data:

library(tibble)

df1 <- data_frame(
  gr = c('a', 'b', 'c'),
  values = list(1:2, 3:4, 5:6)
)

# A tibble: 3 x 2
  gr    values   
  <chr> <list>   
1 a     <int [2]>
2 b     <int [2]>
3 c     <int [2]>

Goal:

df2 <- data_frame(
  gr = c('a', 'b', 'c'),
  V1 = c(1, 3, 5),
  V2 = c(2, 4, 6)
)

# A tibble: 3 x 3
  gr       V1    V2
  <chr> <dbl> <dbl>
1 a        1.    2.
2 b        3.    4.
3 c        5.    6.

Current method:

unnest(df1) %>% 
  group_by(gr) %>% 
  mutate(r = paste0('V', row_number())) %>% 
  spread(r, values)

解决方案

with tidyr 1.0.0 you can do :

library(tidyr)
df1 <- tibble(
  gr = c('a', 'b', 'c'),
  values = list(1:2, 3:4, 5:6)
)

unnest_wider(df1, values)
#> New names:
#> * `` -> ...1
#> * `` -> ...2
#> New names:
#> * `` -> ...1
#> * `` -> ...2
#> New names:
#> * `` -> ...1
#> * `` -> ...2
#> # A tibble: 3 x 3
#>   gr     ...1  ...2
#>   <chr> <int> <int>
#> 1 a         1     2
#> 2 b         3     4
#> 3 c         5     6

^{Created on 2019-09-14 by the reprex package (v0.3.0)}

The output is verbose here because the elements that were unnested horizontally (the vector elements) were not named, and unnest_wider doesn't want to guess silently.

We can name them beforehand to avoid it :

df1 %>%
  dplyr::mutate(values = purrr::map(values, setNames, c("V1","V2"))) %>%
  unnest_wider(values)
#> # A tibble: 3 x 3
#>   gr       V1    V2
#>   <chr> <int> <int>
#> 1 a         1     2
#> 2 b         3     4
#> 3 c         5     6

Or just use suppressMessages() or purrr::quietly()

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