r - 如何统计和计算 R data.frame 中两列的百分比？

Question

在 R 中，我有一个像这样的 data.frame:

df1 <- data.frame(
  grade = rep(LETTERS[1:5], 4),
  sex = c(rep("male", 5), rep("female", 5), rep("male", 4), rep("female", 6)),
  class = c(rep(1, 10), rep(2, 10))
)

df1

   grade    sex class
1      A   male     1
2      B   male     1
3      C   male     1
4      D   male     1
5      E   male     1
6      A female     1
7      B female     1
8      C female     1
9      D female     1
10     E female     1
11     A   male     2
12     B   male     2
13     C   male     2
14     D   male     2
15     E female     2
16     A female     2
17     B female     2
18     C female     2
19     D female     2
20     E female     2

我想计算每个类(class)的性别百分比并制作另一个数据框，例如:

Class Male_percent Female_percentage 
1     50%          50% 
2     40%          60%

有人可以教我怎么做吗？ 这个问题以前可能有人问过，但我不知道这个问题的关键词是什么。如果我再次问同样的问题，我很抱歉。

Answer 1

你可以试试

 prop.table(table(df1[3:2]),1)*100
 #    sex
 #class female male
 #  1     50   50
 #  2     60   40

或者使用data.table

 library(data.table)
 setDT(df1)[, .N, by = .(class, sex)
          ][, .(Male_percent = paste0(100 * N[sex == 'male'] / sum(N), '%'), 
              Female_percent = paste0(100 * N[sex == 'female'] / sum(N), '%')), 
           by = class] 
 #   class Male_percent   Female_percent
 #1:     1          50%              50%
 #2:     2          40%              60%

或者使用dplyr

 library(dplyr)
 df1 %>%
     group_by(class) %>% 
     summarise(Male_Percent= sprintf('%d%%', 100*sum(sex=='male')/n()), 
             Female_Percent = sprintf('%d%%', 100*sum(sex=='female')/n()))
 #    class Male_Percent Female_Percent
 #1     1          50%            50%
 #2     2          40%            60%

或者

  library(sqldf)
  res1 <- sqldf('select class, 
            100*sum(sex=="male")/count(sex) as m, 
            100*sum(sex=="female")/count(sex) as f,
            "%" as p
             from df1
             group by class')
   sqldf("select class,
           m||p as Male_Percent, 
           f||p as Female_Percent 
           from res1")
   #  class Male_Percent Female_Percent
   #1     1          50%            50%
   #2     2          40%            60%

更新

根据@G.Grothendieck的评论，sqldf评论可以简化为

   sqldf("select class,
        (100 * avg(sex = 'male')) || '%' as Male_Percent,
        (100 * avg(sex = 'female')) || '%' as Female_Percent
        from df1 group
         by class")
   #     class Male_Percent Female_Percent
   #1     1        50.0%          50.0%
   #2     2        40.0%          60.0%