使用 R 中的列表替换值

Question

I have a large dataframe, and am trying to count up the scores of many questions. Here is some sample data.

Q1 = c("apple", "banana", "cider", "muffin", "chocolate")
Q2 = c("orange", "kiwi", "calzone", "cupcake", "cake")
ID = c("P1", "P2", "P3", "P4", "P5")

mydf = data.frame(Q1,Q2,ID)

answer_key = c("apple", "kiwi", "pizza", "dessert", "cake")

I've been trying to use ifelse and %in% for the whole dataframe

mydf = ifelse(mydf %in% answer_key, 1,0)

but it doesn't work, and it returns a vector when I need a dataframe. I just want to replace my values without having to do this for each question because there are many:

mydf$Q1 <-ifelse(mydf$Q1 == "apple", 1, 0)
mydf$Q2 <-ifelse(mydf$Q2 == "kiwi", 1, 0)

Answer 1

Perhaps this is what you're looking for?

library(dplry)
mydf %>%
   mutate(across(Q1:Q2,~ +(. %in% answer_key)))
  Q1 Q2 ID
1  1  0 P1
2  0  1 P2
3  0  0 P3
4  0  0 P4
5  0  1 P5

---

Or a bit messy with base R:

mydf[,c("Q1","Q2")] <- sapply(mydf[,c("Q1","Q2")],function(x) +(x%in%answer_key))
mydf
  Q1 Q2 ID
1  1  0 P1
2  0  1 P2
3  0  0 P3
4  0  0 P4
5  0  1 P5

Answer 2

I hope this is what you are looking for:

library(dplyr)

mydf %>%
  mutate(across(Q1:Q2, ~ ifelse(.x %in% answer_key, 1, 0)))

  Q1 Q2 ID
1  1  0 P1
2  0  1 P2
3  0  0 P3
4  0  0 P4
5  0  1 P5