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[英]How to efficiently nest() and unnest_wider() in R's tidyverse
[英]how to nest a column into itself in tidyverse
library(tidyverse)
为什么会产生列表列“ am”:
mtcars %>%
group_by(cyl) %>%
mutate(am=list(mtcars[,'am']))
但不是:
mtcars %>%
group_by(cyl) %>%
nest() %>%
mutate(am=list(mtcars[,'am']))
错误:与STRSXP不兼容
我意识到这是一个人为的示例,但这与我正在研究的内容有关。 突变不会超出其环境范围吗?
mtcars %>% group_by(cyl) %>% nest()
## # A tibble: 3 × 2
## cyl data
## <dbl> <list>
## 1 6 <tibble [7 × 10]>
## 2 4 <tibble [11 × 10]>
## 3 8 <tibble [14 × 10]>
有三行,因此您需要的任何列也必须有三个元素。
如果您希望每行都包含完整的am
列,则可以按行进行突变,这将分别评估每行的mutate
调用,
mtcars %>% group_by(cyl) %>% nest() %>% rowwise() %>% mutate(am = list(mtcars$am))
## Source: local data frame [3 x 3]
## Groups: <by row>
##
## # A tibble: 3 × 3
## cyl data am
## <dbl> <list> <list>
## 1 6 <tibble [7 × 10]> <dbl [32]>
## 2 4 <tibble [11 × 10]> <dbl [32]>
## 3 8 <tibble [14 × 10]> <dbl [32]>
或不rowwise
,只需为每行重复所需的列表:
mtcars %>% group_by(cyl) %>% nest() %>% mutate(am = rep(list(mtcars$am), n()))
## # A tibble: 3 × 3
## cyl data am
## <dbl> <list> <list>
## 1 6 <tibble [7 × 10]> <dbl [32]>
## 2 4 <tibble [11 × 10]> <dbl [32]>
## 3 8 <tibble [14 × 10]> <dbl [32]>
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