Combining matrices (above and below diagonal)

Question

Say I have this matrices:

emp <- matrix(nrow = 13, ncol = 13)
emp2 <- matrix(nrow = 13, ncol = 13)

emp[lower.tri(emp)] <- 2
emp2[lower.tri(emp)] <- 3

And I want to combine them so below the diagonal, I have all values = 2 and above all values = 3. I have managed to produce this as such (then the result is just the emp matrix).

emp[upper.tri(emp)] <- t(emp2[lower.tri(emp2)])

However, now I would like to store the result and make a function for this (after all the matrices I want to use are inside elements of a list). Do you know how can I store this in a new matrix? Or perhaps a better alternative.

I hope I have provided a reproducible enough example, otherwise, let me know.

Thank you!

Answer 1

I think you can use pmax with option na.rm = TRUE

> pmax(emp, t(emp2), na.rm = TRUE)
      [,1] [,2] [,3] [,4] [,5] [,6] [,7] [,8] [,9] [,10] [,11] [,12] [,13]
 [1,]   NA    3    3    3    3    3    3    3    3     3     3     3     3
 [2,]    2   NA    3    3    3    3    3    3    3     3     3     3     3
 [3,]    2    2   NA    3    3    3    3    3    3     3     3     3     3
 [4,]    2    2    2   NA    3    3    3    3    3     3     3     3     3
 [5,]    2    2    2    2   NA    3    3    3    3     3     3     3     3
 [6,]    2    2    2    2    2   NA    3    3    3     3     3     3     3
 [7,]    2    2    2    2    2    2   NA    3    3     3     3     3     3
 [8,]    2    2    2    2    2    2    2   NA    3     3     3     3     3
 [9,]    2    2    2    2    2    2    2    2   NA     3     3     3     3
[10,]    2    2    2    2    2    2    2    2    2    NA     3     3     3
[11,]    2    2    2    2    2    2    2    2    2     2    NA     3     3
[12,]    2    2    2    2    2    2    2    2    2     2     2    NA     3
[13,]    2    2    2    2    2    2    2    2    2     2     2     2    NA

Answer 2

Just wrap the logic in a function and Map over the list.

> fx <- \(e1, e2) {
+   e1[upper.tri(e1)] <- t(e2[lower.tri(e2)])
+   e1
+ }
> lst <- list(list(emp, emp, emp), list(emp2, emp2, emp2))
> Map(fx, lst[[1]], lst[[2]])
[[1]]
      [,1] [,2] [,3] [,4] [,5] [,6] [,7] [,8] [,9] [,10] [,11] [,12] [,13]
 [1,]   NA    3    3    3    3    3    3    3    3     3     3     3     3
 [2,]    2   NA    3    3    3    3    3    3    3     3     3     3     3
 [3,]    2    2   NA    3    3    3    3    3    3     3     3     3     3
 [4,]    2    2    2   NA    3    3    3    3    3     3     3     3     3
 [5,]    2    2    2    2   NA    3    3    3    3     3     3     3     3
 [6,]    2    2    2    2    2   NA    3    3    3     3     3     3     3
 [7,]    2    2    2    2    2    2   NA    3    3     3     3     3     3
 [8,]    2    2    2    2    2    2    2   NA    3     3     3     3     3
 [9,]    2    2    2    2    2    2    2    2   NA     3     3     3     3
[10,]    2    2    2    2    2    2    2    2    2    NA     3     3     3
[11,]    2    2    2    2    2    2    2    2    2     2    NA     3     3
[12,]    2    2    2    2    2    2    2    2    2     2     2    NA     3
[13,]    2    2    2    2    2    2    2    2    2     2     2     2    NA

[[2]]
      [,1] [,2] [,3] [,4] [,5] [,6] [,7] [,8] [,9] [,10] [,11] [,12] [,13]
 [1,]   NA    3    3    3    3    3    3    3    3     3     3     3     3
 [2,]    2   NA    3    3    3    3    3    3    3     3     3     3     3
 [3,]    2    2   NA    3    3    3    3    3    3     3     3     3     3
 [4,]    2    2    2   NA    3    3    3    3    3     3     3     3     3
 [5,]    2    2    2    2   NA    3    3    3    3     3     3     3     3
 [6,]    2    2    2    2    2   NA    3    3    3     3     3     3     3
 [7,]    2    2    2    2    2    2   NA    3    3     3     3     3     3
 [8,]    2    2    2    2    2    2    2   NA    3     3     3     3     3
 [9,]    2    2    2    2    2    2    2    2   NA     3     3     3     3
[10,]    2    2    2    2    2    2    2    2    2    NA     3     3     3
[11,]    2    2    2    2    2    2    2    2    2     2    NA     3     3
[12,]    2    2    2    2    2    2    2    2    2     2     2    NA     3
[13,]    2    2    2    2    2    2    2    2    2     2     2     2    NA

[[3]]
      [,1] [,2] [,3] [,4] [,5] [,6] [,7] [,8] [,9] [,10] [,11] [,12] [,13]
 [1,]   NA    3    3    3    3    3    3    3    3     3     3     3     3
 [2,]    2   NA    3    3    3    3    3    3    3     3     3     3     3
 [3,]    2    2   NA    3    3    3    3    3    3     3     3     3     3
 [4,]    2    2    2   NA    3    3    3    3    3     3     3     3     3
 [5,]    2    2    2    2   NA    3    3    3    3     3     3     3     3
 [6,]    2    2    2    2    2   NA    3    3    3     3     3     3     3
 [7,]    2    2    2    2    2    2   NA    3    3     3     3     3     3
 [8,]    2    2    2    2    2    2    2   NA    3     3     3     3     3
 [9,]    2    2    2    2    2    2    2    2   NA     3     3     3     3
[10,]    2    2    2    2    2    2    2    2    2    NA     3     3     3
[11,]    2    2    2    2    2    2    2    2    2     2    NA     3     3
[12,]    2    2    2    2    2    2    2    2    2     2     2    NA     3
[13,]    2    2    2    2    2    2    2    2    2     2     2     2    NA