How can I get a element in list in R?

Question

I am new to R, I want to get a element in a list which is element in another list, like this:

> a<-list(foo=1:4,bar=7:9) 
> a 
$foo
[1] 1 2 3 4

$bar 
[1] 7 8 9

How can I get the "3" in foo? In python, I use something like

a["foo"][1]

to get the element, but can anybody tell me the corresponding method in R?

Answer 1

另一个选择是$以名称提取list元素，然后使用[

a$foo[1]

Answer 2

use

a[[1]][[3]]

or

a[[c(1,3)]]

to get element 3 in foo.