Hi,
I'm using colSums and rowSums to sum the first dimensions of arrays. It works ok but the resulting object is different. See
> a3d <- array(rnorm(120, mean=2), dim=c(20,6,1)) > dim(colSums(a3d)) [1] 6 1 > dim(rowSums(a3d)) NULL > class(colSums(a3d)) [1] "matrix" > class(rowSums(a3d)) [1] "numeric"
I was expecting rowSums to preserve the array class and the relevant dimensions (1,20).
The main problem is with arrays where the third dimension (or higher) is > 1. colSums preserve the array but rowSums concatenate the results:
> a3d <- array(rnorm(120, mean=2), dim=c(20,3,2))
> rowSums(a3d)
[1] 8.894178 11.932361 15.231601 12.374629 11.823671 10.564709 9.065166
[8] 13.900264 13.331756 9.351242 11.989821 7.643745 9.923288 8.169997
[15] 12.124624 16.711742 11.414150 15.221880 12.053734 13.368988
> colSums(a3d)
[,1] [,2]
[1,] 44.80941 29.49216
[2,] 42.18339 39.81121
[3,] 39.90528 38.89010Is this on purpose ?
Regards
EJ
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