2-Dimensional List in R

Question

I would like a "2-dimensional list" where entry (i, j) stores a vector/matrix of unknown size. Something like

my2Dlist[i,j] <- runif(k)

where k varies with i and j. What is the data structure I am looking for?

Thank you.

The components of dataframes can be lists containing anything (e.g. matrices or vectors) — Cettt
– Cettt, Commented Apr 17, 2019 at 19:25
@Cettt Could you explain further? I tried creating an empty 2x2 data frame test <-data.frame(matrix(ncol=2,nrow=2)) and then test[1,1] <- c(1,1), but R didn't dig it... — P. May
– P. May, Commented Apr 17, 2019 at 19:53
I do not see how a data frame satisfies my needs. The columns of a data frame can be heterogeneous, but I cannot (or cannot see how to) store a matrix in mydataframe[i,j]. — P. May
– P. May, Commented Apr 17, 2019 at 20:42
Eventually you can use a list of lists with my2Dlist[[i]][[j]] to access an element at the position (i, j). — jogo
– jogo, Commented Apr 18, 2019 at 4:41

P. May · Accepted Answer · 2019-04-17 21:04:45Z

Self-Answer: The solution I found is as follows. If I want a 2x2 list, I write

my2Dlist <- as.list(1:4) dim(my2Dlist) <- c(2,2)

One can then store anything in the components, for example

my2Dlist[[1,2]] <- c(1, 1, 2, 3, 5, 8)

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