Get access to the first row of a list in R

Question

Consider a list in R, for example

A=list()
A[[1]]=c(1,2)
A[[2]]=c(3,4)

Is it possible to return a vector which gives the first element of each entry of the list (here c(1,3))?

And as a extension: What, if the elements of the list are not just vectors but matrices. Is it possible to get the vector that contains the first element of the second row for each matrix?

Answer 1

 A=list()
 A[[1]]=c(1,2)
 A[[2]]=c(3,4)
 A[[3]]=c(5,6)

 A
 # [[1]]
 # [1] 1 2

 # [[2]]
 # [1] 3 4

 # [[3]]
 # [1] 5 6

I. First Solution using sapply() function for just first elements

 sapply(A,'[[',1)
 # [1] 1 3 5

For Getting lets say 1st, 3rd, 4th elements of each nested list. Not applicable in this example

 sapply(A,`[`,c(1,3,4))

II. Second Solution using for loop

 for(i in 1:length(A)){
 print (A[[i]][1])
 }
 # [1] 1
 # [1] 3
 # [1] 5

Answer 2

Try this below:

sapply(A, "[", 1)