Function to create a new variable not working in R - r

Question

I am creating a function to help me quickly recode variables into numerical values, as a form of practice. The idea behind creating the function is to quickly recode several values into numerical form, for any length. If a dataset is really long for instance, the function in theory should recode all of these values without having to manually type out each condition in which to recode it into a specific value.
For instance:
levels(d$letters)
[1] a b c d
The general form of the function is to:
d$letters.recode[d$letters == "a"] <- 1
d$letters.recode[d$letters == "b"] <- 2
d$letters.recode[d$letters == "c"] <- 3
And using this function:
rc.f <- function(a, b){
x <- levels(a)
y <- length(a)
b <- NA
for (i in 1:y){
z <- b[a==x[i]] <- i
}
}
In theory, the idea is that this function should create another variable, where a is recoded as 1, b is recoded as 2 and so on.
However when I run rc.f(d$letters, d$letters.recode), no new variables are created in the dataset, and the function does not return an error.
Any ideas?
Thanks.
Another example dataset d:
Say for a list of respondents they are assigned a category depending on their region:
Respondent Region
1 d
2 b
3 g
4 c
5 e
6 c
7 f
8 a
I am looking for a way to recode d$Region into a numerical value, to d$Region.R.
Using the same function as above, I am wondering whether I can use the function to create another variable in the dataframe, by inputting d$Region and d$Region.R into the function. So recoding a,b,c,[...],g into 1,2,3,[...],7.

Answer 1

If you want to a,b,f,d as 1,2,4,3 then use following
I have updated your code for function rc.f a little bit
Removed second argument b, since we are giving b <- NA ,so we do not need second argument
We do not need other variable to store the value of b , so i removed z
Since every argument is not factor so we need to coerce it into factor
we do not need y , we can directly put length(a) in for loop condition
and last but not the least the last line is the output of the function unless we use return, so there i putted b in last
The code is
rc.f <- function(a)
{
a<-as.factor(a)
x <- levels(a)
b <- NA
for (i in 1:length(a))
{
b[a==x[i]] <- i
}
b
}
let us take an example
> l<-c("a","b","b","a","a","g","h","y","f","v","h","j","f","d","a","s","s","s")
> l
[1] "a" "b" "b" "a" "a" "g" "h" "y" "f" "v" "h" "j" "f"
[14] "d" "a" "s" "s" "s"
> rc.f(l)
[1] 1 2 2 1 1 5 6 10 4 9 6 7 4 3 1 8 8 8
If you want a,b,f,d as 1,2,6,4 then use following
rc.f <- function(a)
{
a<-as.factor(a)
b <- NA
for (i in 1:26)
{
b[a==letters[i]] <- i
}
b
}
lets take an example
> l<-c("a","b","b","a","a","g","h","y","f","v","h","j","f","d","a","s","s","s")
> l
[1] "a" "b" "b" "a" "a" "g" "h" "y" "f" "v" "h" "j" "f" "d"
[15] "a" "s" "s" "s"
> rc.f(l)
[1] 1 2 2 1 1 7 8 25 6 22 8 10 6 4 1 19 19 19