R Language Data frames Convert all columns of a data.frame to character class
Example
A common task is to convert all columns of a data.frame to character class for ease of manipulation, such as in the cases of sending data.frames to a RDBMS or merging data.frames containing factors where levels may differ between input data.frames.
The best time to do this is when the data is read in - almost all input methods that create data frames have an options stringsAsFactors which can be set to FALSE.
If the data has already been created, factor columns can be converted to character columns as shown below.
bob <- data.frame(jobs = c("scientist", "analyst"),
pay = c(160000, 100000), age = c(30, 25))
str(bob)
'data.frame': 2 obs. of 3 variables: $ jobs: Factor w/ 2 levels "analyst","scientist": 2 1 $ pay : num 160000 100000 $ age : num 30 25
# Convert *all columns* to character
bob[] <- lapply(bob, as.character)
str(bob)
'data.frame': 2 obs. of 3 variables: $ jobs: chr "scientist" "analyst" $ pay : chr "160000" "1e+05" $ age : chr "30" "25"
# Convert only factor columns to character
bob[] <- lapply(bob, function(x) {
if is.factor(x) x <- as.character(x)
return(x)
})
