Convert qualitative numeric variables into factors in R

Question

I have the following code already READY, which my advisor passed to me

fatores=c("Year","Month","DayofWeek","DayofMonth")

dadosFatores=apply(dados[,fatores],2,XXXX)

dados[,XXXX]=dadosFatores

In exercise it says that I should change only the XXXX by something that makes sense and returns what the function asks, ie, convert the variables in question into factors.

I tried to replace it with as.factor, without great success.

Someone could help ?

Answer 1

Changing my answer, actually there is a previous problem, you would have to use the lapply instead of apply, because apparently the apply will play everything to an array and convert to character before returning to the data.frame (had not tested the code before).

Generating fictitious data to illustrate:

dados <- data.frame(x = 1:10)
dados[, fatores] <- rep(c("a", "b", "c", "d"),10)
str(dados)
data.frame':    10 obs. of  5 variables:
 $ x         : int  1 2 3 4 5 6 7 8 9 10
 $ Year      : chr  "a" "b" "c" "d" ...
 $ Month     : chr  "c" "d" "a" "b" ...
 $ DayofWeek : chr  "a" "b" "c" "d" ...
 $ DayofMonth: chr  "c" "d" "a" "b" ...

With apply (doesn’t work):

dados[,fatores]= apply(dados[,fatores], 2, as.factor)
str(dados)
'data.frame':   10 obs. of  5 variables:
 $ x         : int  1 2 3 4 5 6 7 8 9 10
 $ Year      : chr  "a" "b" "c" "d" ...
 $ Month     : chr  "c" "d" "a" "b" ...
 $ DayofWeek : chr  "a" "b" "c" "d" ...
 $ DayofMonth: chr  "c" "d" "a" "b" ...

With the lapply (works):

dados[,fatores]= lapply(dados[,fatores], as.factor)
str(dados)
'data.frame':   10 obs. of  5 variables:
 $ x         : int  1 2 3 4 5 6 7 8 9 10
 $ Year      : Factor w/ 4 levels "a","b","c","d": 1 2 3 4 1 2 3 4 1 2
 $ Month     : Factor w/ 4 levels "a","b","c","d": 3 4 1 2 3 4 1 2 3 4
 $ DayofWeek : Factor w/ 4 levels "a","b","c","d": 1 2 3 4 1 2 3 4 1 2
 $ DayofMonth: Factor w/ 4 levels "a","b","c","d": 3 4 1 2 3 4 1 2 3 4

If an error appears in the above code, put the error message and a playable example so we can understand what the problem is and the result of head(dados) and str(dados) in your question to see what the object is like