How to perform calculations on all matrices in an array simultaneously

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I have a large array and I need to find the rowSums() for all the matrices within the array simultaneously, but individually. Whenever I do:

rowSums(array1[ , ,1:1000])

I get the total sum of all the values in each row across the entire array. What I need is:

rowSums(array1[ , ,1])

But that only gives me the rowSums() for 1 matrix and I need it for all of them. Essentially, I need to convert the array into a new array where the matrices are row sums of the previous matrices.

I could do it manually, but that would take me hours due to the size of the array and I know there is a simple solution I am to R-illiterate to see.

Thank you so much.

r arrays
1 Answers

We can use apply with MARGIN = 3

apply(array1, 3, rowSums)
      [,1] [,2] [,3]
[1,]    9   27   45
[2,]   12   30   48

which is the same as doing individually

> rowSums(array1[, , 1])
[1]  9 12
> rowSums(array1[, , 2])
[1] 27 30
> rowSums(array1[, , 3])
[1] 45 48

data

array1 <- array(1:18, c(2, 3, 3))
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