Question

我正在尝试将数字划分为多个类别以创建新列。基本上是尝试根据分数创建字母等级（“ A”，“ B”，“ C”，“ D”，“ F”）。

我在以下代码中再现了与遇到问题的数据帧类似的数据帧。

df <- tibble(score = rnorm(20:100, n = 150))

我为添加成绩列而编写的代码如下：

df_with_grade <- df %>% 
  mutate(Grade = if (score >= 90) {
    "A"
  } else if (score >= 80){
    "B"
  } else if (score >= 70){
    "C"
  } else if (score >= 60){
    "D"
  } else {
    "F"
  }
  )

代码执行时显示警告：

Warning messages:
1: In if (score >= 90) { :
  the condition has length > 1 and only the first element will be used
2: In if (score >= 80) { :
  the condition has length > 1 and only the first element will be used
3: In if (score >= 70) { :
  the condition has length > 1 and only the first element will be used
4: In if (score >= 60) { :
  the condition has length > 1 and only the first element will be used

结果是，所有分数均被分配为“ F”

Answer 1

怎么样

cut(df$score,breaks=c(0,6:10)*10,labels=rev(LETTERS[c(1:4,6)]))

？ rev(LETTERS[c(1:4,6)])可能太聪明了，不能在c("F","D","C","B","A")上保存个字符...

Answer 2

如评论中所建议，您可以使用case_when：

df_with_grade <- df %>% 
  mutate(Grade = case_when(score >= 90 ~ "A",
                           score >= 80 ~ "B",
                           score >= 70 ~ "C",
                           score >= 60 ~ "D",
                                     TRUE ~ "F"))

Answer 3

您不能使用ifelse，它仅适用于二进制条件。像下面那样使用切割，

df$Grade = cut(df$score,
breaks=c(0,60,70,80,90,100),
label=c("F","D","C","B","A"),
include.lowest =TRUE)

Answer 4

仅为说明您可以使用ifelse。

df_with_grade <- df %>% 
  mutate(Grade = 
ifelse(score>= 90, "A", 
  ifelse(score>=80, "B", 
    ifelse(score>=70, "C", 
      ifelse(score>=60, "D", 
        "F")))) 
    )

使用if else语句添加列

4 个答案: