# [R] function sum for array

R. Michael Weylandt michael.weylandt at gmail.com
Thu Nov 17 21:39:12 CET 2011

```It might not be as general as you have in mind, but this works:

X = array(1:24, c(2,3,4))
rowSums(X, dims = 2)

Combined with aperm() it's pretty powerful.

Michael

On Thu, Nov 17, 2011 at 11:24 AM, Simone Salvadei
> I'm looking for a function that allows to sum the elements of an array
> along a dimension that can be different from the classical ones (rows or
> columns).
>
> Let's suppose for example that:
>
> - A is an array with dimensions 2 x 3 x 4
> - I want to compute B, a 2 x 3 matrix with elements equal to the sum of the
> corrensponding elements on each of the 3 strata.
>
> I've tried to use   apply(A,3,sum) but the result is a vector, not a matrix.
> Another solution is a less elegant
>
> B=matrix(rep(0,6),ncol=3)
> for(t in 1:4) B = B + A[ , , t]
>
> May anybody help?
> S
>
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>
> Faculty of Economics
> Department of Financial and Economic Studies and Quantitative Methods
> University of Rome Tor Vergata
> e-mail: simone.salvadei at uniroma2.it <federico.belotti at uniroma2.it>
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> <http://www.econometrics.it/>
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