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

[Henrique Dallazuanna]

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
>
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-- 
Henrique Dallazuanna
Curitiba-Paraná-Brasil
25° 25' 40" S 49° 16' 22" O