Changing class of data frame columns using strings

Question

I have a dataframe where all the columns have the character class but many of the columns should be of numeric or integer class. I also have a character vector containing the desired class for each column e.g.

classes <- c("integer", "integer", "numeric", "character", "logical", "numeric", ... )

I am looking for a way to set the class of each column quickly using this classes vector without looping.

I was hoping there would be a way to do this similar to naming, e.g.

names(df) <- names

where names is a character vector, or in my case

class(df) <- classes

Answer 1

Use Map:

df <- data.frame(V1=letters[1:3],
                 V2=c("1","2","3"),
                 V3=c("1.1","2.2","3.3"),stringsAsFactors=FALSE)

classes <- c("character","integer","numeric")

str(df)
#'data.frame':   3 obs. of  3 variables:
# $ V1: chr  "a" "b" "c"
# $ V2: chr  "1" "2" "3"
# $ V3: chr  "1.1" "2.2" "3.3"

df[] <- Map(`class<-`, df, classes)

str(df)
#'data.frame':   3 obs. of  3 variables:
# $ V1: chr  "a" "b" "c"
# $ V2: int  1 2 3
# $ V3: num  1.1 2.2 3.3