Conditional dataframe mutations

Question

I have a large data frame that has a lot of string values that I want to clean.

Example:

    students <- data.frame(name = c("John", "Jerry", "Bill", "Tom", "Mary", "Bill"),
                       class = c("A", "B", "-", "#NA", "A", "low"), stringsAsFactors = FALSE)

I want every student who is not in class A,B or C to be set to D. My current solution is:

'%!in%' <- function(x,y)!('%in%'(x,y))
for(i in 1:nrow(students)) {
  if(students$class[i] %!in% c("A", "B", "C")) {
    students$class[i] <- "D"
  }
}

Is there a better solution than this, preferably with piping as there are a number of columns like this?

Thanks!

Answer 1

We can do this without a loop as assignment is vectorized

students$class[students$class %!in% c("A", "B", "C")] <- "D"
students
#   name class
#1  John     A
#2 Jerry     B
#3  Bill     D
#4   Tom     D
#5  Mary     A
#6  Bill     D