Hello,
Hui Du wrote
>
> Hi All,
>
> Suppose I have the following codes:
>
> x = data.frame(A = rnorm(20), B = rnorm(20), C = rnorm(20))
> a = list()
> a[["1.1"]] = x
> a[["1.2"]] = x
>
> b = list()
> b[["1.1"]] = c("A", "B")
> b[["1.2"]] = c("B", "C")
>
>
> Now I want to apply b to a like this, for each element of 'a', only select
> the corresponding columns listed in 'b'. For example, after that
> operation,
>
> a[["1,1"]] become subset(a[["1.1"]], select = c("A", "B"))
>
> a[["1,2"]] become subset(a[["1.1"]], select = c("B", "C"))
>
> Do you know how to do it without looping?
>
> Thanks.
>
>
> HXD
>
>
> [[alternative HTML version deleted]]
>
> ______________________________________________
> R-help@ mailing list
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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.
>
If it's a list and you want to avoid a loop, think about lapply or similar.
(Tip: you don't want sapply.)
?lapply
lapply(names(a), function(i) subset(a[[i]], select = b[[i]]))
It's your code, but "lapplied" to all elements of your objects.
Hope this helps,
Rui Barradas
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