list indexing

Hello

I've got a question about  list indexing. If anyone can help or point
in the direction of some documentation, that'd be great. I've checked
the Introduction to R and R language definition.

Say you have a list of vectors:

x_list(c("a","b","c"),c("a","b","c","d"),c("a","b"),c("a","b","c","d","e"))

x

[[1]]
[1] "a" "b" "c"

[[2]]
[1] "a" "b" "c" "d"

[[3]]
[1] "a" "b"

[[4]]
[1] "a" "b" "c" "d" "e"
Indexing single list components is fine using [[i]] and elements
within using [[i]][j] but what if you want to get some information,
for instance vector length or attributes of the components, across (or
should that be down) the top level components. You can do it by
looping across 1:length(list):

store <- numeric(0)
for(components in 1:length(x)) store <-

c(store,length(x[[components]]))

store

[1] 3 4 2 5
I know it's only two lines of code. I  guess I'm wondering whether
there is something that does what I'd expect from length(x[[1:4]]) if
[[i]] allowed multiple indices.

Thanks,
David Orme.

Hello

I've got a question about  list indexing. If anyone can help or point
in the direction of some documentation, that'd be great. I've checked
the Introduction to R and R language definition.

Say you have a list of vectors:

x_list(c("a","b","c"),c("a","b","c","d"),c("a","b"),c("a","b","c","d","e"))

x

[[1]]
[1] "a" "b" "c"

[[2]]
[1] "a" "b" "c" "d"

[[3]]
[1] "a" "b"

[[4]]
[1] "a" "b" "c" "d" "e"
Indexing single list components is fine using [[i]] and elements
within using [[i]][j] but what if you want to get some information,
for instance vector length or attributes of the components, across (or
should that be down) the top level components. You can do it by
looping across 1:length(list):

store <- numeric(0)
for(components in 1:length(x)) store <-

c(store,length(x[[components]]))

store

[1] 3 4 2 5
I know it's only two lines of code. I  guess I'm wondering whether
there is something that does what I'd expect from length(x[[1:4]]) if
[[i]] allowed multiple indices.

Thanks,
David Orme.