How to declare list object with M elements

Question

I want to declare a list containing M 3 by 3 matrices. If I knew the number M in advance, then I can declare such list by:

elm <- matrix(NA,3,3) ## Say M = 7 myList <- list(elm,elm,elm,elm,elm,elm,elm)  

This method becomes cumbersome if M is large. What's worse this method does not work if I do not know the value of M in advance. If I want to declare a vector of length M, I can do it by calling:

myVec <- rep(NA,M) 

even if I do not know the value of M in advance. Is there similar way to declare a list of size M?

Answer 1

Maybe this:

myls <- vector("list", length = S)

Answer 2

Try

mylist <- rep(list(elm),7) 

which, for S=3, gives

[[1]]      [,1] [,2] [,3] [1,]   NA   NA   NA [2,]   NA   NA   NA [3,]   NA   NA   NA  [[2]]      [,1] [,2] [,3] [1,]   NA   NA   NA [2,]   NA   NA   NA [3,]   NA   NA   NA  [[3]]      [,1] [,2] [,3] [1,]   NA   NA   NA [2,]   NA   NA   NA [3,]   NA   NA   NA 

By the way, identical(matrix(NA,3,3),matrix(,3,3)) is true, since matrices are initialized to NA by default. See ?matrix.