Replacing characters in an array with numbers

Question

I have read in data from an excel file, and made it into a vector. I then made it into a 3d array.

The vector that forms the array, and also inside the array now has in it characters, like this:

D <- c('g', 't', NA, 'd')
nPeriods = 3
column.names = c('aaa', 'bbb')
row.names = c('jjj', 'hhh')
threeD.names = c(1:nPeriods)
E = array(c(D), dim=c(2, 2, nPeriods),
          dimnames = list(row.names, column.names, threeD.names))

However, now I want to assign 'g', 't', etc as variables with starting values, e.g.

g = 5
t = 2
d = 7

But the only way I know how to do this is by manually figuring out which element of the array it is and assigning it like that, e.g.

E[1,1,]=5

When it's a large matrix that's going to be difficult and annoying to find the corresponding position every time I refer to an element. I know that each element of the vector (that is not NA) is unique, so I wondered, is there a shortcut for referring to each element of the array? (Maybe something in the apply family? but there are so many of them).

I will also need to refer later to them to loop over nPeriods. Yesterday someone showed me I can do this with:

for (i in 2:nPeriods){
  C[1,1,i]=C[1,1,i-1]*2
}

But in real life my matrix might be quite large so I'd rather just be able to refer with d, t, etc.

Answer 1

This task is more manageable in a list. You can use the following:

# Example data
D <- c('g', 't', NA, 'd')
nPeriods = 3
column.names = c('aaa', 'bbb')
row.names = c('jjj', 'hhh')
threeD.names = c(1:nPeriods)
E = array(c(D), dim=c(2, 2, nPeriods),
          dimnames = list(row.names, column.names, threeD.names))

# Convert array to list
array_list <- lapply(seq(dim(E)[3]), function(x) E[,,x])

# Re-assign values
array_converted <- lapply(array_list, function(x){
  x <- ifelse(x == "g", 5, x) # your conversion values
  x <- ifelse(x == "t", 2, x)
  x <- ifelse(x == "d", 7, x)
  x <- apply(x, 2, as.numeric) # Ensures values are numeric
  return(x)
})

# For final format as array (if you want)
final_array <- simplify2array(array_converted)