[R] Effeciently sum 3d table

[David Winsemius]

On Apr 16, 2012, at 2:43 PM, David A Vavra wrote:

> Thanks Petr,
>
> I'm after T1 + T2 + T3 + ...

Which would be one number ... i.e. the result you originally said you  
did not want.

> and your solution is giving a list of n items
> each containing sum(T[i]). I guess I should have been clearer in  
> stating
> what I need.

Or even now you _could_ be clearer. Do you want successive partial  
sums? That would yield to:

Reduce("+", listoftables, accumaulate=TRUE)




>
> Cheers,
> DAV	
>
>
>
> -----Original Message-----
> From: r-help-bounces at r-project.org [mailto:r-help-bounces at r-project.org 
> ] On
> Behalf Of Petr Savicky
> Sent: Monday, April 16, 2012 11:07 AM
> To: r-help at r-project.org
> Subject: Re: [R] Effeciently sum 3d table
>
> On Mon, Apr 16, 2012 at 10:28:43AM -0400, David A Vavra wrote:
>> I have a large number of 3d tables that I wish to sum
>> Is there an efficient way to do this? Or perhaps a function I can  
>> call?
>>
>> I tried using do.call("sum",listoftables) but that returns a single  
>> value.
>
>>
>> So far, it seems only a loop will do the job.
>
> Hi.
>
> Use lapply(), for example
>
>  listoftables <- list(array(1:8, dim=c(2, 2, 2)), array(2:9,  
> dim=c(2, 2,
> 2)))
>  lapply(listoftables, sum)
>
>  [[1]]
>  [1] 36
>
>  [[2]]
>  [1] 44
>
> Hope this helps.
>
> Petr Savicky.
>
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> and provide commented, minimal, self-contained, reproducible code.

David Winsemius, MD
West Hartford, CT