[R] names not inherited in functions

[Gabor Grothendieck]

Within a function deparse(substitute(x)) will give the name of x, as a character
variable.  Search the archives for
  deparse substitute
to find many examples.

On 8/17/07, david dav <davamaillist at gmail.com> wrote:
> 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
> > >
> > > ______________________________________________
> > > R-help at stat.math.ethz.ch 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.
> >
>
> ______________________________________________
> R-help at stat.math.ethz.ch 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.
>