[R] How to assess object names within a function in lapply or l_ply?

[Heinz Tuechler]

Thank you, Henrique,

my example was simplified. In a more complexe 
function I want to use the objects, not just 
their names. In your solution, I have to adapt 
the function itself, depending on the name of the 
data.frame, which I would like to avoid.

Thanks,
Heinz


At 13:36 28.09.2009, Henrique Dallazuanna wrote:
>You can use names insteed:
>
>DF <- data.frame(a=1:3, b=2:4)
>lapply(names(DF), function(x){
>                                 print(x)
>                                 DF[x]
>                         })
>
>On Mon, Sep 28, 2009 at 8:22 AM, Heinz Tuechler <tuechler at gmx.at> wrote:
> > Dear All,
> >
> > to produce output of several columns of a data frame, I tried to use lapply
> > and also l_ply. In both cases, I would like to print a header line
> > containing also the name of the respective column in the data frame.
> >
> > For example, I would like the following
> >
> > lapply(data.frame(a=1:3, b=2:4), function(x) print(deparse(substitute(x))))
> >
> > to produce:
> > [1] "a"
> > [1] "b"
> >
> > and not, what it actually does:
> > [1] "X[[1L]]"
> > [1] "X[[2L]]"
> > $a
> > [1] "X[[1L]]"
> >
> > $b
> > [1] "X[[2L]]"
> >
> > or with l_ply (plyr package)
> > l_ply(data.frame(a=1:3, b=2:4), function(x) print(deparse(substitute(x))))
> >
> > to produce:
> > [1] "a"
> > [1] "b"
> >
> > and not, what it actually does:
> > [1] ".data[[i]]"
> > [1] ".data[[i]]"
> >
> > Is this possible?
> >
> > Thanks,
> > Heinz
> >
> > ______________________________________________
> > R-help at r-project.org 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.
> >
>
>
>
>--
>Henrique Dallazuanna
>Curitiba-Paraná-Brasil
>25° 25' 40" S 49° 16' 22" O