Convert factor to character

In R, you used sometimes functions to convert vectors to another format with as.character, as.factor or as.numeric.

However, you need to be careful when using the function as.numeric on a factor. Indeed, if the factor contains factor number, it will convert them to the level number and not convert the writing number from your factor.

Here is a short example:

library(data.table)
set.seed(23) #set.seed to have the same random value as in this example
to_convert <- factor(runif(1:10, min = 0, max = 100))

print(levels(to_convert))

[1] "22.3072855733335" "33.1896589370444" "42.3720560967922" "57.6603659661487"
[5] "71.072455169633"  "81.9448956055567" "84.052187949419"  "96.3544549420476"
[9] "97.8130409261212" "99.6611237060279"

data.table(factor_to_convert = to_convert, 
           using_as_numeric_only = as.numeric(to_convert), 
           using_as_character_first = as.numeric(as.character(to_convert)))

So, be careful when you are using factor with numerical levels and you want to convert them.