[R] summing array elements

[Erich Neuwirth]

> arr<-1:72
> dim(arr)<-c(2,4,3,3)
> apply(arr,1:2,sum)
     [,1] [,2] [,3] [,4]
[1,]  297  315  333  351
[2,]  306  324  342  360
> apply(arr,3:4,sum)
     [,1] [,2] [,3]
[1,]   36  228  420
[2,]  100  292  484
[3,]  164  356  548
>

apply(arr,1:2,sum)
will sum all elements arr(i1,i2,..)
for each single combination of the first and the second index
over all possible combinations of the third and fourth index.




On 5/27/2011 12:06 AM, marco milella wrote:
> Hi to everybody
> I have an array with dimensions 2,4,3,3.
> Wanting to sum the matrices in the first two dimensions, I'm trying to use
> the "apply" function, but with no results. Have to say I'm quite new with R
> syntax.
> tx in advance
> 
> marco
> 
> 	[[alternative HTML version deleted]]
> 
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