how to create two-dimension list in R

Question

I want to transfer matlab code into R, ctlist is a vector, matlab code as folllowed:

telist{i,j}=ctlist;
[value,number]=max(ctlist);

I just wonder there is "data structure" in R like the telist{i,j} in matlab

Answer 1

You can have infinitely nested lists:

list1 <- list()

list1[[1]] <- list()

list[[1]][[1]] <- list()

and so on...

But for a more practical example, say you want 2 lists having each 3 lists inside:

my.list.1 <- list()
my.list.1[[1]] <- list()
my.list.1[[2]] <- list()
my.list.1[[3]] <- list()

my.list.2 <- list()
my.list.2[[1]] <- list()
my.list.2[[2]] <- list()
my.list.2[[3]] <- list()

Is there a specific syntax to create those list structures in no time?

As per Richard Skriven's comment, replicate can do that. Example: my.lists <- replicate(n=5, expr=list()) will create 5 lists all at once and store them under the name my.lists.

Filling in the lists

You could indeed fill in any of those lists or sub-lists with vectors or matrices or arrays. For instance:

my.list.1[[1]][[1]] <- c(1,5,3,3,5,3)
my.list.1[[1]][[2]] <- matrix(0, nrow=10, ncol=10)

There are no constraints, really.

Dynamically extending lists

You could also add dynamically elements to your lists, in loops for instance:

my.list <- list() # we're creating a new one, but the following loop could
                  # be using a pre-existing list with data already inside
for(i in 1:10) {
  my.list[[length(my.list) + 1]] <- (i*1):(i*200)
}

---

Arrays

If however all your data are all of the same type structured in "rectangular/cubic" ways, you can use multidimensional arrays.

> array(data = NA, dim = c(3,3,3))
, , 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