R: Simplifying code to convert letter grades to numeric grades

Question

I have written a function in R that will convert a data frame containing letter grades into numeric grades. I then use sapply() on each column of the data frame. Is there a

Answer 1

Here is a pretty fast hash approach that shines the more grades you have:

library(qdap)

grvec <- list("A+"=4.3,"A"=4,"A-"=3.7,"B+"=3.3,"B"=3,"B-"=2.7,
    "C+"=2.3,"C"=2,"C-"=1.7,"D+"=1.3,"D"=1,"D-"= 0.7, "F"=0)

dat[] <- lapply(dat, lookup, list2df(grvec)[, c(2:1)])

##   final_exam quiz_avg homework_avg
## 1        2.0      4.0            4
## 2        1.7      2.7            4
## 3        1.3      3.3            4
## 4        3.3      3.3            4
## 5        0.0      3.3            4
## 6        3.0      3.7            4