converting multiple columns from character to numeric format in r

Question

What is the most efficient way to convert multiple columns in a data frame from character to numeric format?

I have a dataframe called DF with all character variables.

I would like to do something like

for (i in names(DF){
    DF$i <- as.numeric(DF$i)
}

Thank you

Answer 1

You could try

DF <- data.frame("a" = as.character(0:5),
                 "b" = paste(0:5, ".1", sep = ""),
                 "c" = letters[1:6],
                 stringsAsFactors = FALSE)

# Check columns classes
sapply(DF, class)

#           a           b           c 
# "character" "character" "character" 

cols.num <- c("a","b")
DF[cols.num] <- sapply(DF[cols.num],as.numeric)
sapply(DF, class)

#          a           b           c 
#  "numeric"   "numeric" "character"