R-在几列上应用DPLYR函数

Question

i具有一个数据框架，其中〜150k行和77个类别变量，例如以下形式。我如何找到每个类别的分数和计数

一个数字变量和77个分组变量

students<-data.frame(ID = c("A","B","C","D"), Gender = c("M","F","F","F"), Socioeconomic = c("Low","Low","Medium","High"), Subject = c("Maths","Maths","Science", "Science"),
                    Scores = c(45,98, 50,38))

也就

students %>% group_by(Gender) %>% summarise(Mean.score = mean(Scores), Count = length(ID))
students %>% group_by(Socioeconomic) %>% summarise(Mean.score = mean(Scores), Count = length(ID))
students %>% group_by(Subject) %>% summarise(Mean.score = mean(Scores), Count = length(ID))```

Answer 1

这有两个选项：

library(tidyverse)
# map successively over each categorical column
map(students %>% select(-Scores, -ID) %>% names() %>% set_names(),
    ~ students %>% 
      group_by_at(.x) %>% 
      summarise(Mean.score = mean(Scores), 
                Count = n())
)

$Gender
# A tibble: 2 x 3
  Gender Mean.score Count
  <fct>       <dbl> <int>
1 F              62     3
2 M              45     1
$Socioeconomic
# A tibble: 3 x 3
  Socioeconomic Mean.score Count
  <fct>              <dbl> <int>
1 High                38       1
2 Low                 71.5     2
3 Medium              50       1
$Subject
# A tibble: 2 x 3
  Subject Mean.score Count
  <fct>        <dbl> <int>
1 Maths         71.5     2
2 Science       44       2

# Convert to long format, group, then summarize
students %>% 
  gather(key, value, -ID, -Scores) %>% 
  group_by(key, value) %>% 
  summarise(Count=n(),
            Mean.score=mean(Scores))

  key           value   Count Mean.score
  <chr>         <chr>   <int>      <dbl>
1 Gender        F           3       62  
2 Gender        M           1       45  
3 Socioeconomic High        1       38  
4 Socioeconomic Low         2       71.5
5 Socioeconomic Medium      1       50  
6 Subject       Maths       2       71.5
7 Subject       Science     2       44