I have data as follows:

```
tableA <- structure(c(0L, 0L, 6L, 0L, 6L, 0L, 3L, 0L, 0L), dim = c(3L, 
3L), dimnames = structure(list(c("0.3", "0.4", 
"0.6"), c("A", "B", "C")), names = c("", "")), class = "table")

      A B C
  0.3 0 0 3
  0.4 0 6 0
  0.6 6 0 0

tableB <-structure(c(0L, 1L, 2L, 0L, 3L, 0L, 3L, 2L, 0L), dim = c(3L, 
3L), dimnames = structure(list(c("0.3", "0.4", 
"0.6"), c("A", "B", "C")), names = c("", "")), class = "table")

      A B C
  0.3 0 0 3
  0.4 1 3 2
  0.6 2 0 0

```

I would like to replace all zeroes in `tableA` with positive values in `tableB` if they are available and somehow mark them.

What would be the easiest way to achieve this?

Desired output:

```
      A B C
  0.3 0 0 3
  0.4 1 6 2
  0.6 6 0 0

```

The added issue is that I would somehow like to know which values were replaced, but that seems difficult to realise.