Referencing factors through their equivalent numeric level

[Kaushik Krishnan]

Hey folks

I'm sorry for bringing what must be a very simple question to R-help,
but after some research I haven't been able to find a solution to my
problem.

Suppose I create a simple factor:
[code]
> x<-c("A","B","B","C","A")
> x
[1] "A" "B" "B" "C" "A"
> x <- as.factor(x)
> x
[1] A B B C A
Levels: A B C
[/code]

Now, when I see this factor in terms of its numeric level values, I get
[code]
> as.numeric(x)
[1] 1 2 2 3 1
[/code]

Suppose I have
[code]
y <- 2
[/code]

I want the numeric value of y to reference the level of factor x. That
is, I am looking for a function (`foo') so that I will get the
following
[code]
foo(y) #or maybe foo(y,x)
[1] B
[/code]

I can think of a roundabout way of doing through a user defined
function, but I am sure that there is a built-in function that offers
this functionality. I'd be grateful if someone could tell me what that
function is.

Thanks in advance

--
Kaushik Krishnan
([hidden email])

______________________________________________
[hidden email] mailing list
https://stat.ethz.ch/mailman/listinfo/r-help
PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.

[Berend Hasselman]

On 02-05-2012, at 07:22, Kaushik Krishnan wrote:

> Hey folks
>
> I'm sorry for bringing what must be a very simple question to R-help,
> but after some research I haven't been able to find a solution to my
> problem.
>
> Suppose I create a simple factor:
> [code]
>> x<-c("A","B","B","C","A")
>> x
> [1] "A" "B" "B" "C" "A"
>> x <- as.factor(x)
>> x
> [1] A B B C A
> Levels: A B C
> [/code]
>
> Now, when I see this factor in terms of its numeric level values, I get
> [code]
>> as.numeric(x)
> [1] 1 2 2 3 1
> [/code]
>
> Suppose I have
> [code]
> y <- 2
> [/code]
>
> I want the numeric value of y to reference the level of factor x. That
> is, I am looking for a function (`foo') so that I will get the
> following
> [code]
> foo(y) #or maybe foo(y,x)
> [1] B
> [/code]
>
> I can think of a roundabout way of doing through a user defined
> function, but I am sure that there is a built-in function that offers
> this functionality. I'd be grateful if someone could tell me what that
> function is.

Maybe this?

levels(x)[y]

Berend

______________________________________________
[hidden email] mailing list
https://stat.ethz.ch/mailman/listinfo/r-help
PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.

[Kaushik Krishnan]

That did it! Thanks very much Berend.

On Wed, May 2, 2012 at 4:19 AM, Berend Hasselman <[hidden email]> wrote:

>
> On 02-05-2012, at 07:22, Kaushik Krishnan wrote:
>
>> Hey folks
>>
>> I'm sorry for bringing what must be a very simple question to R-help,
>> but after some research I haven't been able to find a solution to my
>> problem.
>>
>> Suppose I create a simple factor:
>> [code]
>>> x<-c("A","B","B","C","A")
>>> x
>> [1] "A" "B" "B" "C" "A"
>>> x <- as.factor(x)
>>> x
>> [1] A B B C A
>> Levels: A B C
>> [/code]
>>
>> Now, when I see this factor in terms of its numeric level values, I get
>> [code]
>>> as.numeric(x)
>> [1] 1 2 2 3 1
>> [/code]
>>
>> Suppose I have
>> [code]
>> y <- 2
>> [/code]
>>
>> I want the numeric value of y to reference the level of factor x. That
>> is, I am looking for a function (`foo') so that I will get the
>> following
>> [code]
>> foo(y) #or maybe foo(y,x)
>> [1] B
>> [/code]
>>
>> I can think of a roundabout way of doing through a user defined
>> function, but I am sure that there is a built-in function that offers
>> this functionality. I'd be grateful if someone could tell me what that
>> function is.
>
> Maybe this?
>
> levels(x)[y]
>
> Berend
>

--
Kaushik Krishnan
([hidden email])

______________________________________________
[hidden email] mailing list
https://stat.ethz.ch/mailman/listinfo/r-help
PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.