[R] Standard deviation for each element in a set of matrices

[David Winsemius]

On Dec 4, 2009, at 1:27 PM, Gray Calhoun wrote:

> Hi Muhammad,
>  Load the data from all of the files into an array (probably using a
> for loop), then call apply on the resulting array: ie

I like that idea a lot and it does not need an explicit loop:

apply( array(c(File1, File2, File3), dim=c(3,3,3) )  , 1:2, sd)



I had come up with this rather messy solution before seeing your much  
more elegant one:

matrix( apply(sapply(list(File1, File2, File3), "["), 1,sd),  
nrow(File1), ncol(File1) )

-- 
David
>
> ## replace the first line with code to load your data
>> rr <- array(c(rep(1:3,3), rep(4:6,3), rep(7:9,3)), c(3,3,3))
>> apply(rr, c(1,2), sd)
>     [,1] [,2] [,3]
> [1,]    3    3    3
> [2,]    3    3    3
> [3,]    3    3    3
>
> --Gray
>
> On Fri, Dec 4, 2009 at 11:56 AM, Muhammad Rahiz
> <muhammad.rahiz at ouce.ox.ac.uk> wrote:
>> Hello R-users,
>>
>> I would like to know how to find the standard deviation for each  
>> element in
>> a set of matrices.
>>
>> Given the following files,
>>
>>   File1    File2    File3
>>   1 1 1   4 4 4   7 7 7
>>   2 2 2   5 5 5   8 8 8
>>   3 3 3   6 6 6   9 9 9
>>
>> I want to calculate the standard deviation for every cell in the  
>> file (I'm
>> using gridded data). The desired output is
>>
>>   Output
>>   3 3 3
>>   3 3 3
>>   3 3 3
>>
>>
>> Thanks.
>>
>> Muhammad
>>
>> --
>> 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
>>
>> ______________________________________________
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>> PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
>> and provide commented, minimal, self-contained, reproducible code.
>>
>
>
>
> -- 
> Gray Calhoun
>
> Assistant Professor of Economics
> Iowa State University
>
> ______________________________________________
> 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.

David Winsemius, MD
Heritage Laboratories
West Hartford, CT