for loop iteration over multiple subarrays - r

Question

I have the variable assignments
N <- 10
H <- 10
K <- 2 # number of subarrays
perms <- 10
I set up an empty array as follows:
pop <- array(dim = c(c(perms, N), K))
Then I assign character labels:
haps <- as.character(1:H)
Now, I assign probabilities:
probs <- rep(1/H, H)
I then create a 'for' loop:
for(j in 1:perms){
for(i in 1:K){
pop[i,j] <- sample(haps, size = N, replace = TRUE, prob = probs)
}
}
'pop' should now contain character labels from 1:H across both subarrays. Instead, I end up with an error "incorrect number of subscripts on matrix."
I am not sure why R is producing the error.
Any assistance is appreciated.

Answer 1

You gave 2 subscripts to the 3 dimensional vector pop. Also the dimensions of the sample wouldn't have matched the dimensions of the slice of pop even if you had added a 3rd subscript because the order was wrong.
dim(pop)
[1] 10 10 2
You may have wanted this:
for(j in 1:perms){
for(i in 1:K){
pop[1:10,j,i] <- sample(haps, size = N, replace = TRUE, prob = probs)
}
}
pop
, , 1
[,1] [,2] [,3] [,4] [,5] [,6] [,7] [,8] [,9] [,10]
[1,] "6" "8" "8" "6" "3" "3" "1" "9" "7" "8"
[2,] "7" "10" "5" "3" "7" "10" "7" "1" "5" "8"
[3,] "9" "7" "1" "4" "1" "3" "2" "7" "6" "5"
[4,] "6" "8" "9" "4" "9" "7" "10" "9" "7" "2"
[5,] "1" "3" "2" "6" "10" "3" "3" "9" "10" "6"
[6,] "9" "3" "8" "1" "6" "6" "4" "8" "8" "9"
[7,] "9" "2" "2" "2" "3" "9" "8" "6" "10" "10"
[8,] "9" "5" "3" "8" "3" "4" "1" "6" "8" "4"
[9,] "10" "8" "1" "3" "10" "2" "5" "10" "6" "4"
[10,] "2" "1" "8" "10" "5" "5" "7" "8" "7" "6"
, , 2
[,1] [,2] [,3] [,4] [,5] [,6] [,7] [,8] [,9] [,10]
[1,] "1" "10" "10" "7" "3" "6" "3" "2" "4" "1"
[2,] "8" "5" "10" "8" "3" "6" "6" "6" "8" "2"
[3,] "1" "6" "1" "5" "6" "3" "6" "1" "7" "9"
[4,] "7" "10" "5" "5" "7" "5" "3" "3" "10" "1"
[5,] "7" "3" "6" "8" "3" "9" "6" "2" "7" "3"
[6,] "1" "9" "4" "9" "1" "1" "10" "4" "3" "9"
[7,] "9" "3" "10" "1" "2" "2" "2" "3" "5" "4"
[8,] "8" "10" "8" "6" "9" "6" "9" "9" "2" "4"
[9,] "4" "6" "1" "1" "6" "5" "6" "6" "10" "3"
[10,] "5" "9" "9" "7" "9" "6" "4" "2" "10" "9"
Though it seems strange to me that you want the numbers in haps and therefore pop to be characters, but I assume that you have your reasons.
This is a column-wise assignment of the samples. I'm not sure if it matters, but if you prefer row-wise then you can do the index like this:
pop[j,1:10,i]