[R] building a list in a loop

[William Dunlap]

Does the following do what you want?
> d <- list() # empty list
> for(i in 1:8) if (i %% 2 == 0) {
     newElement <- structure(list(i), names=LETTERS[i])
     d <- c(d, newElement)
  }
> str(d)
List of 4
 $ B: int 2
 $ D: int 4
 $ F: int 6
 $ H: int 8




Bill Dunlap
TIBCO Software
wdunlap tibco.com

On Fri, Jun 5, 2015 at 1:40 AM, carol white via R-help <r-help at r-project.org
> wrote:

> It might be an easy question but how to construct correctly a list in a
> loop?
>
> The following doesn't work
> before starting the loopd = NULL#in the loop, 1st iteration
> d = list(d,c(1,2,3)d[[1]]
> NULL
>
> [[2]]
> [1] 1 2 3#in the loop, 2nd iterationd=list(d,c(4,5,6)d
> [[1]]
> [[1]][[1]]
> NULL
>
> [[1]][[2]]
> [1] 1 2 3
>
>
> [[2]]
> [1] 4 5 6
> the goal is to have the result of d= list(c(1,2,3),c(4,5,6)) where the
> list components are not known out of the loop.
> d[[1]]
> [1] 1 2 3
>
> [[2]]
> [1] 4 5 6
> Moreover, how to name the components of the list in the loop while
> constructing as the names are not known out of the loop, either? note that
> the name of the component is stored in a variable in the loop
>
> d = NULL#name1 contains the name for c(1,2,3), how to give the name below?
> d = list(d,c(1,2,3)
> Thanks
>
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