R: Multidimensional array index assignment

Question

Consider the following array assignments:

temp=array(list(),2)
temp[[2]][[2]]=c("a","b")
temp[[1]][[2]]="c"

This produces the following result:

temp
[[1]]
[1] NA  "c"

[[2]]
[[2]][[1]]
NULL

[[2]][[2]]
[1] "a" "b"

Instead, I want the result to be:

temp
[[1]]
[[1]][[1]]
NULL
[[1]][[2]]
[1] "c"

[[2]]
[[2]][[1]]
NULL

[[2]][[2]]
[1] "a" "b"

How do I make the assignment so that the former is produced rather than the latter?

In my actual code I create the contents of this array using loops and other functions with variable outputs. I can't manually solve the problem in the middle of my function; I need some way to insert the result directly to the proper place in the array. — Logister
– Logister, Commented Sep 22, 2014 at 1:48

Rich Scriven · Accepted Answer · 2014-09-22 02:11:06Z

3

You can initialize the list(s) with replicate instead of array. Lists and arrays behave differently

x <- replicate(2, list())
x[[1]][[2]] <- "c"
x[[2]][[2]] <- c("a", "b")
x

Note:

is.array(x)
# [1] FALSE
sapply(x, is.array)
# [1] FALSE FALSE

answered Sep 22, 2014 at 1:59

Rich Scriven

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