R help - Nov 2009 - categorisation of continuous variables in R

Dear all,

I'm looking for a function comparable to switch, to categorize a
continuous variable in a few levels. Off course that can be done with
a series of ifelse statements, but that looks rather clumsy. I looked
at switch, but couldn't figure out how to use it for this. I guess
that's not possible, as it only works with characters or integers, not
with intervals.

Basically, I'm looking for a clean way to do :
test <- runif(10,1,100)

testFunc <-function(x){
x <-  ifelse(test<10,"lowest",
        ifelse(10<=test & test <50,"low",
          ifelse(50<=test & test <90,"high",
            ifelse(90<=test & test<100,"highest",NA)
          )
        )
      )
return(as.factor(x))
}

testFunc(test)

Thank you in advance

Never mind, found the function :

cut(test,breaks=c(0,10,50,90,100),labels=c("lowest","low","high","highest"),include.lowest=T,right=F)

Cheers
Joris

On Mon, Nov 23, 2009 at 2:14 PM, joris meys <jorismeys at gmail.com>
wrote:
> Dear all,
>
> I'm looking for a function comparable to switch, to categorize a
> continuous variable in a few levels. Off course that can be done with
> a series of ifelse statements, but that looks rather clumsy. I looked
> at switch, but couldn't figure out how to use it for this. I guess
> that's not possible, as it only works with characters or integers, not
> with intervals.
>
> Basically, I'm looking for a clean way to do :
> test <- runif(10,1,100)
>
> testFunc <-function(x){
> x <- ?ifelse(test<10,"lowest",
> ? ? ? ?ifelse(10<=test & test <50,"low",
> ? ? ? ? ?ifelse(50<=test & test <90,"high",
> ? ? ? ? ? ?ifelse(90<=test & test<100,"highest",NA)
> ? ? ? ? ?)
> ? ? ? ?)
> ? ? ?)
> return(as.factor(x))
> }
>
> testFunc(test)
>
> Thank you in advance
>

On Nov 23, 2009, at 8:14 AM, joris meys wrote:
> Dear all,
>
> I'm looking for a function comparable to switch, to categorize a
> continuous variable in a few levels.
?cut

> Off course that can be done with
> a series of ifelse statements, but that looks rather clumsy. I looked
> at switch, but couldn't figure out how to use it for this. I guess
> that's not possible, as it only works with characters or integers, not
> with intervals.
>
> Basically, I'm looking for a clean way to do :
> test <- runif(10,1,100)
 > test <- runif(10,1,100)
 > testcut <- cut(test, breaks=c(-Inf, 10, 50, 90, 100))
 > table(testcut)
testcut
(-Inf,10]   (10,50]   (50,90]  (90,100]
         1         4         5         0

>
> testFunc <-function(x){
> x <-  ifelse(test<10,"lowest",
>        ifelse(10<=test & test <50,"low",
>          ifelse(50<=test & test <90,"high",
>            ifelse(90<=test & test<100,"highest",NA)
>          )
>        )
>      )
> return(as.factor(x))
> }
>
> testFunc(test)
>
> Thank you in advance

-- 
David Winsemius, MD
Heritage Laboratories
West Hartford, CT