Example on class "factor"

# This code demonstrates how to use factor  # First, let's show the survey results survey.result <- c("F", "F", "D", "A-", "A+", "B-", "B", "B", "C", "C-")  # This is the order of the possible responses order.ascend <- c("F", "D", "C-", "C", "B-", "B", "B+", "A-", "A", "A+")  # Now, let's make them into factor result <- factor(x=survey.result, levels=order.ascend, ordered=TRUE)  # We can also change the element of the factor # > result # [1] F  F  D  A- A+ B- B  B  C  C- # Levels: F < D < C- < C < B- < B < B+ < A- < A < A+ result[3] <- "A" # And the result becomes: # > result # [1] F  F  A  A- A+ B- B  B  C  C- # Levels: F < D < C- < C < B- < B < B+ < A- < A < A+  # We can also remove the class label result.integer <- unclass(result) # Here is what you will get # > result.integer  # [1]  1  1  9  8 10  5  6  6  4  3 # attr(,"levels")  # [1] "F"  "D"  "C-" "C"  "B-" "B"  "B+" "A-" "A"  "A+"   # Of course, we can return the label to them  class(result.integer) <- "factor"  # We simply say, make the class to be "factor", and that's it!