How to append the results found in a for loop and if statement

Question

I am practicing looping over the values that are found in a particular column (Z_SCORE). however I want to now append the result of each iteration into a data frame. Can I get some assistance on how I could go about to do that. The new data frame will be variables and the name of the column being comment. Any edits to my code are welcome.

variables$comment<-data.frame()

for (i in grade$Z_SCORE){
  if (i <= -0.5){
    print("good")
  } else if (i >=0.5){
    print("bad")
  }else
   print("neutral")
}

My desired output is a data frame with something like:

Comment
good
good
bad
neutral

I know I can do it using thee code below (A), however I want to learn how to use a for loop in r

A<-grades%>%
  mutate(comment = case_when(Z_SCORE <= -0.5 ~ "good",
                                 Z_SCORE >= 0.5 ~ "bad",
                                 T ~ "neutral"))

Answer 1

Generally speaking, an approach like this would work:

# Prepare output
comments <- list(rep("", length(grade$Z_SCORE))

# then fill the list
for (i in seq_along(grade$Z_SCORE)){
  # if grade$Z_SCORE has 7 items, this loop will be run with i = 1, then 2, then 3... then 7.
  # we want to compare to the value of the i'th element of grade$Z_SCORE
  j <- grade$Z_SCORE[i]
  comments[i] <- if (j <= -0.5){
      "good"
    } else if (j >=0.5){
      "bad"
    } else {"neutral"}
}

# you can now add the filled list to a data frame if needed