使用 mutate() 和 ifelse()

Question

Very simple question. Is there any disadvantage to using the 2nd approach outlined below versus approach 1? Or are they effectively identical. (I'm partial to approach 2 as I deal with some complicated conditioning of variables, and find it easier to track piping the variable from one line to the next, but concerned that it might be poor coding practice)

library(dplyr)

section <- c("MATH111", "MATH111", "ENG111")
grade <- c(78, 93, 56)
student <- c("David", "Kristina", "Mycroft")
gradebook <- data.frame(section, grade, student)
mutate(gradebook, Pass.Fail = ifelse(grade > 60, "Pass", "Fail"))

#approach 1
mutate(gradebook, letter = ifelse(grade %in% 60:69, "D",
                           ifelse(grade %in% 70:79, "C",
                           ifelse(grade %in% 80:89, "B",
                           ifelse(grade %in% 90:99, "A", "F")))))


#approach 2
gradebook$letter<-NA
gradebook <- gradebook %>% 
  mutate(letter=ifelse(grade < 60, "F",letter)) %>% 
  mutate(letter=ifelse(grade >60 & grade< 69, "D",letter)) %>% 
  mutate(letter=ifelse(grade >70 & grade< 79, "C",letter)) %>% 
  mutate(letter=ifelse(grade >80 & grade< 89, "B",letter)) %>% 
  mutate(letter=ifelse(grade >90 & grade< 99, "A",letter))
gradebook

Answer 1

It seems there are some typo, but if you try using dplyr::mutate , in this case, dplyr::case_when will helps.

gradebook %>%
  mutate(letter = case_when(
    grade < 60 ~ "F",
    grade < 70 ~ "D",
    grade < 80 ~ "C",
    grade < 90 ~ "B",
    grade < 100 ~ "A",
    T ~ NA_character_
    ))

  section grade  student letter
1 MATH111    78    David      C
2 MATH111    93 Kristina      A
3  ENG111    56  Mycroft      F