R help - May 2011 - summing array elements

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

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On Fri, May 27, 2011 at 10:06 AM, marco milella <vrukol at gmail.com>
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.
Tell apply() which dimensions you want to keep, in this case 3 and 4

R> m<-array(1, dim=c(2,4,3,3))
R> apply(m,3:4,sum)
     [,1] [,2] [,3]
[1,]    8    8    8
[2,]    8    8    8
[3,]    8    8    8

    -thomas

-- 
Thomas Lumley
Professor of Biostatistics
University of Auckland

> 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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