How to convert categorical variable to numerical in R?

Question

I am very new to R

I have the following dataset

age    sex    bmi children smoker    region   charges  sex_N
1  19 female 27.900        0    yes southwest 16884.924 female
2  18   male 33.770        1     no southeast  1725.552   male
3  28   male 33.000        3     no southeast  4449.462   male
4  33   male 22.705        0     no northwest 21984.471   male
5  32   male 28.880        0     no northwest  3866.855   male
6  31 female 25.740        0     no southeast  3756.622 female

I want to predict charges based on the other columns however other columns are categorical how do I change them to numeric variables?

I tried doing costs$sex_N <- as.factor(costs$sex) but that did not give me the correct column as you can see above?

also, if columns which has unique values greater than 2, how to convert them? please help!

Answer 1

Here are two base R options that may help

> transform(
+   costs,
+   sex_N = as.integer(as.factor(sex_N))
+ )
  age    sex    bmi children smoker    region   charges sex_N
1  19 female 27.900        0    yes southwest 16884.924     1
2  18   male 33.770        1     no southeast  1725.552     2
3  28   male 33.000        3     no southeast  4449.462     2
4  33   male 22.705        0     no northwest 21984.471     2
5  32   male 28.880        0     no northwest  3866.855     2
6  31 female 25.740        0     no southeast  3756.622     1

or

> transform(
+   costs,
+   sex_N = match(sex_N, sex_N)
+ )
  age    sex    bmi children smoker    region   charges sex_N
1  19 female 27.900        0    yes southwest 16884.924     1
2  18   male 33.770        1     no southeast  1725.552     2
3  28   male 33.000        3     no southeast  4449.462     2
4  33   male 22.705        0     no northwest 21984.471     2
5  32   male 28.880        0     no northwest  3866.855     2
6  31 female 25.740        0     no southeast  3756.622     1