R help - Dec 2009 - Standard deviation for each element in a set of matrices

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

Muhammad -
    Here's one way:

files = c('File1','File2','File3')
themats = lapply(files,read.table)
ans = matrix(0,3,3)
for(i in 1:3)for(j in 1:3)ans[i,j] = sd(sapply(themats,function(x)x[i,j]))

    Here's another

files = c('File1','File2','File3')
themats = lapply(files,read.table)
ans =
outer(1:3,1:3,Vectorize(function(i,j)sd(sapply(themats,function(x)x[i,j]))))


 					- Phil Spector
 					 Statistical Computing Facility
 					 Department of Statistics
 					 UC Berkeley
 					 spector at stat.berkeley.edu


On Fri, 4 Dec 2009, Muhammad Rahiz 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
>
> ______________________________________________
> 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.
>

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

## 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
>
> ______________________________________________
> 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.
>


-- 
Gray Calhoun

Assistant Professor of Economics
Iowa State University