[R] how to do something like symptoms==c('a', 'e', 'z')

[Chuck Cleland]

RenE J.V. Bertin wrote:
> I find myself doing lots of tests like
> 
> 
>>subset( data, symptoms=='a' | symptoms=='e' | symptoms=='z' .... )
> 
> 
> with symptoms one of the factors contained in the data frame.
> 
> and I wonder if there is not an existing operator or function which implements this sort of repeated conditional in a more space-efficient fashion, something like

   How about something like this:

mydata <- data.frame(Y = runif(100), X = rep(letters[1:5], 20))

subset(mydata, X %in% c("a", "c", "d"))

>>subset( data, symptoms==c('a','e','z') )

subset(data, symptoms %in% c("a", "e", "z"))

> 
> (which is incorrect unless symptoms is, in this case, an integer multiple of 3 long).
> 
> Is there, or if not, is there a more efficient/elegant way than 
> 
> select.elements <- function(data, lst)
> {
> 	slctn <- data == lst[1]
> 	for( e in 2:length(lst) ){
> 		slctn <- slctn | (data==lst[e])
> 	}
> 	slctn
> }
> 
> 
> ##> select.elements( 1:10, c(1,5,10) )
>  [1]  TRUE FALSE FALSE FALSE  TRUE FALSE FALSE FALSE FALSE  TRUE
> 
> Thanks,
> RenE
> 
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Chuck Cleland, Ph.D.
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