[R] function "Stack"

[Noah Marconi]

The reshape2 package may be what you're looking for: 
http://cran.r-project.org/web/packages/reshape2/index.html


install.packages("reshape2")
reshape2::melt(df)



On 2014-03-24 12:02, 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 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
> 
> 
> 
> 
> --
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