在purrr :: map（）中使用dplyr :: count（）时出错 [英] Error using dplyr::count() within purrr::map()

问题描述

在此示例中，我想将count（）函数应用于数据集中的每个字符变量。

In this example I want to apply the count() function to every character variable in a dataset.

library(dplyr)
library(purrr)

nycflights13::flights %>% 
    select_if(is.character) %>% 
    map(., count)

但是我收到错误消息：

Error in UseMethod("groups") : no applicable method for 
'groups' applied to an object of class "character"

我不确定解释错误消息或更新我的代码。类似的代码适用于数字变量，但因子变量会产生与字符变量相似的错误消息

I'm not sure how to interpret the error message or update my code. Similar code works for numeric variables, but factor variables produce a similar error message to character variables

nycflights13::flights %>% 
    select_if(is.numeric) %>% 
    map(., mean, na.rm = TRUE)

nycflights13::flights %>% 
    select_if(is.character) %>% 
    mutate_all(as.factor) %>% 
    map(., count)

推荐答案

如果要获取带有值计数的小标题列表，可以使用

If you want a list of tibbles with value counts, you can use

nycflights13::flights %>% 
  select_if(is.character) %>% 
  map(~count(data.frame(x=.x), x))

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