[R] Question on Reduce + rollmean

[Muhammad Rahiz]

Thanks Gabor,

It works alright. But is there alternative ways to perform rollmean 
apart from permutating the data?
Possibly combining the Reduce and rollmean functions?

The easiest but traditional way is

 > (x[[1]]+x[[2]]) / 2
 > (x[[2]]+x[[3]]) / 2
 

Muhammad Rahiz  |  Doctoral Student in Regional Climate Modeling					
Climate Research Laboratory, School of Geography & the Environment	
Oxford University Centre for the Environment
South Parks Road, Oxford, OX1 3QY, United Kingdom 
Tel: +44 (0)1865-285194	 Mobile: +44 (0)7854-625974
Email: muhammad.rahiz at ouce.ox.ac.uk






Gabor Grothendieck wrote:
> Try apply:
>
> library(zoo) # rollmean
>
> # test data
> m <- matrix(1:3, 3, 3)
> x <- list(m, m+3, m+6)
>
> # convert to array
> a <- array(unlist(x), c(3, 3, 3)); a
>
> # apply rollmean and permute to desired form
> aa <- apply(a, 1:2, rollmean, k = 2)
> aperm(aa, c(2, 3, 1))
>
> The last line outputs:
>
>   
>> aperm(aa, c(2, 3, 1))
>>     
> , , 1
>
>      [,1] [,2] [,3]
> [1,]  2.5  2.5  2.5
> [2,]  3.5  3.5  3.5
> [3,]  4.5  4.5  4.5
>
> , , 2
>
>      [,1] [,2] [,3]
> [1,]  5.5  5.5  5.5
> [2,]  6.5  6.5  6.5
> [3,]  7.5  7.5  7.5
>
>
> On Sat, Jan 2, 2010 at 10:00 AM, Muhammad Rahiz
> <muhammad.rahiz at ouce.ox.ac.uk> wrote:
>   
>> Let me rephrase;
>>
>> Given x as
>>
>>     
>>> x
>>>       
>> [[1]]
>>  V1 V2 V3
>> [1,]  1  1  1
>> [2,]  2  2  2
>> [3,]  3  3  3
>>
>> [[2]]
>>  V1 V2 V3
>> [1,]  4  4  4
>> [2,]  5  5  5
>> [3,]  6  6  6
>>
>> [[3]]
>>  V1 V2 V3
>> [1,]  7  7  7
>> [2,]  8  8  8
>> [3,]  9  9  9
>>
>> I'd like to calculate the moving average (interval = 2) i.e.
>>
>> ( x[[1]] + x[[2]] ) / 2
>> ( x[[2]] + x[[3]] ) / 2
>> ... and so on.
>>
>> The desired output will return
>>
>> 2.5 2.5 2.5
>> 3.5 3.5 3.5
>> 4.5 4.5 4.5
>>
>> 5.5 5.5 5.5
>> 6.5 6.5 6.5
>> 7.5 7.5 7.5
>>
>>
>>
>>
>> Muhammad Rahiz  |  Doctoral Student in Regional Climate Modeling
>> Climate Research Laboratory, School of Geography & the Environment
>> Oxford University Centre for the Environment, University of Oxford
>> South Parks Road, Oxford, OX1 3QY, United Kingdom
>> Tel: +44 (0)1865-285194  Mobile: +44 (0)7854-625974
>> Email: muhammad.rahiz at ouce.ox.ac.uk
>>
>>
>>
>> milton ruser wrote:
>>     
>>> Dear M.Rahiz,
>>>
>>> Unfortunatelly I can't reproduce your example.
>>> PLEASE do read the posting guide
>>> http://www.R-project.org/posting-guide.html<http://www.r-project.org/posting-guide.html>
>>>
>>> bests
>>>
>>> milton
>>> On Sat, Jan 2, 2010 at 9:26 AM, Muhammad Rahiz
>>> <muhammad.rahiz at ouce.ox.ac.uk<mailto:muhammad.rahiz at ouce.ox.ac.uk>> wrote:
>>> Hello useRs,
>>>
>>> I'd like to perform a moving average on the dataset, xx. I've tried
>>> combining the functions Reduce and rollmean but it didn't work.
>>>
>>>
>>>       
>>>> r <- function(n) rollmean(n, 2) # where 2 = averaging interval
>>>> output < - Reduce("r", x)
>>>>
>>>>         
>>> Error in f(init, x[[i]]) : unused argument(s) (x[[i]])
>>>
>>> Is there anything wrong with the code in the first place?
>>>
>>> where
>>>
>>>       
>>>> x
>>>>
>>>>         
>>> [[1]]
>>>   V1 V2 V3
>>> [1,]  1  1  1
>>> [2,]  2  2  2
>>> [3,]  3  3  3
>>>
>>> [[2]]
>>>   V1 V2 V3
>>> [1,]  4  4  4
>>> [2,]  5  5  5
>>> [3,]  6  6  6
>>>
>>> [[3]]
>>>   V1 V2 V3
>>> [1,]  7  7  7
>>> [2,]  8  8  8
>>> [3,]  9  9  9
>>>
>>> The moving average is to be performed on
>>>
>>> 1,4,7 = (1+4)/2 , (4+7)/2
>>> 2,5,8 = ..
>>> 3,6,9 = ..
>>>
>>> Thanks
>>>
>>> Muhammad
>>>
>>> --
>>> Muhammad Rahiz  |  Doctoral Student in Regional Climate Modeling
>>> Climate Research Laboratory, School of Geography & the Environment
>>> Oxford University Centre for the Environment, University of Oxford
>>> South Parks Road, Oxford, OX1 3QY, United Kingdom
>>> Tel: +44 (0)1865-285194  Mobile: +44 (0)7854-625974
>>> Email: muhammad.rahiz at ouce.ox.ac.uk<mailto:muhammad.rahiz at ouce.ox.ac.uk>
>>>
>>> ______________________________________________
>>> R-help at r-project.org<mailto:R-help at r-project.org> mailing list
>>> https://stat.ethz.ch/mailman/listinfo/r-help
>>> PLEASE do read the posting guide
>>> http://www.R-project.org/posting-guide.html<http://www.r-project.org/posting-guide.html>
>>> and provide commented, minimal, self-contained, reproducible code.
>>>
>>>
>>>
>>>       
>> ______________________________________________
>> R-help at r-project.org mailing list
>> https://stat.ethz.ch/mailman/listinfo/r-help
>> PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
>> and provide commented, minimal, self-contained, reproducible code.
>>
>>