On Dec 6, 2013, at 11:27 AM, Julio Sergio Santana wrote:
> I have a data frame whose first colum contains the names of the variables
> and whose second colum contains the values to assign to them:
>
> : kkk <- data.frame(vars=c("var1", "var2", "var3"),
> vals=c(10, 20, 30), stringsAsFactors=F)
>
> If I do
>
> : assign(kkk$vars[1], kkk$vals[1])
>
> it works
>
> : var1
> [1] 10
>
> However, if I try with mapply this is what I get:
>
> : mapply(assign, kkk$vars, kkk$vals)
> var1 var2 var3
> 10 20 30
> : var2
> Error: object 'var2' not found
>
> Maybe I have not undestand how mapply and assign work. Do you have
> any comments?
I think you will find that the value returned from the mapply call was a three
element list with the desired names and values ... except you then gave that
enclosing list no name and it will be garbage-collected. If you want to have
'assign' do its magic into the global environment, then you need to supply
'mapply' a MoreArgs argument on the other side of the ellipsis:
Usage:
mapply(FUN, ..., MoreArgs = NULL, SIMPLIFY = TRUE,
USE.NAMES = TRUE)
So what happens if you try this:
mapply(assign, kkk$vars, kkk$vals, MoreArgs = list(envir = .GlobalEnv)
--
David Winsemius
Alameda, CA, USA
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