On Mar 24, 2014, at 9:02 AM, Tham Tran wrote:
> Dears R Users,
>
> I have another question on function "stack".
>
> Given a data frame like:
> df=data.frame(a=c(3,5),b=c(2,8),a=c(9,1),b=c(6,4),check.names=F)
> a b a b
> 3 2 9 6
> 5 8 1 4
>
I did not create your stack function which would have masked the base function.
You would probably not want to do that. Better to name it `mystack` or
somesuch. Yours looks very similar to the code of the utils::stack.
getAnywhere(stack.data.frame)
function (x, select, ...)
{
if (!missing(select)) {
nl <- as.list(1L:ncol(x))
names(nl) <- names(x)
vars <- eval(substitute(select), nl, parent.frame())
x <- x[, vars, drop = FALSE]
}
keep <- unlist(lapply(x, is.vector))
if (!sum(keep))
stop("no vector columns were selected")
if (!all(keep))
warning("non-vector columns will be ignored")
x <- x[, keep, drop = FALSE]
data.frame(values = unlist(unname(x)), ind = factor(rep.int(names(x),
lapply(x, length))), stringsAsFactors = FALSE)
}
> stack(df) # the utils::stack.data.frame
values ind
1 3 a
2 5 a
3 2 b
4 8 b
5 9 a.1
6 1 a.1
7 6 b.1
8 4 b.1
It would be pretty easy to reassign the items with dots in the ind factor and
rbind(stack(df[1:2]), stack(df[3:4]) )
#---------
values ind
1 3 a
2 5 a
3 2 b
4 8 b
5 9 a
6 1 a
7 6 b
8 4 b
--
David.
> I would like to form a new data frame like:
> values ind
> 1 3 a
> 2 5 a
> 3 2 b
> 4 8 b
> 5 9 a
> 6 1 a
> 7 6 b
> 8 4 b
>
> I arrived with the script:
> stack = function (x, ...)
> {
> x = as.list(x)
> keep = unlist(lapply(x, is.vector))
> if (!sum(keep))
> stop("at least one vector element is required")
> if (!all(keep))
> warning("non-vector elements will be ignored")
> x = x[keep]
> data.frame(values = unlist(unname(x)), ind = factor(rep.int(names(x),
> lapply(x, length))), stringsAsFactors = FALSE, ...)
> }
> stack(df, check.names = FALSE)
>
> Do you have any other simple manner to that?
>
> Thanks in advance for your helps!
>
> Tham
>
>
>
>
> --
> View this message in context:
> http://r.789695.n4.nabble.com/function-Stack-tp4687449.html
> Sent from the R help mailing list archive at Nabble.com.
>
> ______________________________________________
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> PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
David Winsemius
Alameda, CA, USA
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