"Mag. Ferri Leberl" <[EMAIL PROTECTED]> wrote in
news:[EMAIL PROTECTED]:
> Dear everybody!
> Is there a command to add elements to an existing list, at best
> excluding the addition of already included ones?
> Thank you in advance.
> Yours,
> Mag. Ferri Leberl
Don't know of one, but it's not that hard to make one.
lone <- c( "r","is", "great")
ltwo <- "great"
lthree <- "but sometimes puzzling"
add.unique<-function(ls1,ls2) {
ifelse (ls2 %in% ls1, return(ls1) , return(c(ls1,ls2)) )
}
> add.unique(lone,ltwo)
[1] "r" "is" "great"
> add.unique(lone,lthree)
[1] "r" "is"
[3] "great" "but sometimes puzzling"
# my puzzlement: until using return(<list argument>),
# only got the first element, "r", back
# I thought ifelse( (.), ls1, .) would evaluate to all of ls1
Technically these are character vectors. If you wanted a more LISP-like
list then you may need to use list() rather than c(). Or you could use
a construction like:
lone[[length(lone)+1]]<-new.element
You really should include example data that lets the reader tell what
structure you are working with and what you expect the function(s) to
return.
--
David Winsemius
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