[R] names not inherited in functions

[david dav]

Dear R list,
After a huge delay, I come back to this question. Using names of
variables inside a function is a problem I run into quite often.
Maybe this little example should help to get my point:
Suppose I want to make a function "llabel" to get the labels of the
variables from a data frame.
If no label is defined, "llabel" should return the name of the variable.

	library(Hmisc)
	v1 <- c(1,2)
	v2 <- c(1,2)
	v3 <- c(1,3)
	tablo <- data.frame(v1,v2,v3)
	rm(v1,v2,v3)

	label(tablo$v1) <- "var1"
	attach(tablo)

# This does the trick on one variable.
	if (label(v1) !="") label(v1)  	else names(data.frame(v1))
	if (label(v2) !="") label(v2)  	else names(data.frame(v2))
	
But if I call this statement in a "llabel" function,

	llabel <- function(var) {
			if (label(var) !="" )
				res <- label(var)
				else res <- names(data.frame(var))
		return (res) }
		
I just get "var"s instead of the names when no label is defined :
	
llabel(v1) # works
llabel(v2) # gives "var" instead of "v2"

Thanks for your help.

David


2007/6/7, Uwe Ligges <ligges at statistik.uni-dortmund.de>:
> Not sure what you are going to get. Can you shorten your functions and
> specify some example data? Then please tell us what your expected result is.
>
> Best,
> Uwe Ligges
>
>
>
>
> david dav wrote:
> > Dear all,
> >
> > I 'd like to keep the names of variables when calling them in a function.
> > An example might help to understand my problem :
> >
> > The following function puts in a new data frame counts and percent of
> > a data.frame called as "tablo"
> > the step " nom.chiffr[1] <- names(vari) " is useless as names from the
> > original data.frame aren't kept in the function environement.
> >
> > Hoping I use appropriate R-vocabulary, I thank you for your help
> >
> > David
> >
> > descriptif <- function (tablo) {
> >       descriptifvar <- function (vari) {
> >               table(vari)
> >               length(vari[!is.na(vari)])
> >               chiffr <- cbind(table(vari),100*table(vari)/(length(vari[!is.na(vari)])))
> >               nom.chiffr <- rep(NA, dim(table(vari)))
> >               if (is.null(names(vari))) nom.chiffr[1] <- paste(i,"") else
> >               nom.chiffr[1] <- names(vari)
> >               chiffr <- data.frame (  names(table(vari)),chiffr)
> >               rownames(chiffr) <- NULL
> >               chiffr <- data.frame (nom.chiffr, chiffr)
> >       return(chiffr)
> >       }
> >
> >       res <- rep(NA, 4)
> >       for (i in 1 : ncol(tablo))
> >               res <- rbind(res,descriptifvar(tablo[,i]))
> >       colnames(res) <- c("variable", "niveau", "effectif", "pourcentage")
> > return(res[-1,])
> > }
> > # NB I used this function on a data.frame with only factors in
> >
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