RE: [R] summary statistics for lists of matrices or dataframes

From: McGehee, Robert <Robert.McGehee_at_geodecapital.com>
Date: Wed 11 May 2005 - 00:18:38 EST


You could try temporarily switching the list to an array, then just run an apply on rows and columns:

> apply(array(do.call("cbind", z), c(dim(z[[1]]), length(z))), c(1, 2),
mean)

Best,
Robert

-----Original Message-----
From: David Kane [mailto:dave@kanecap.com] Sent: Tuesday, May 10, 2005 10:04 AM
To: r-help@stat.math.ethz.ch
Subject: [R] summary statistics for lists of matrices or dataframes

Is there a simple way to calculate summary statistics for all the matrices or dataframes in a list? For example:

> z <- list(matrix(c(2,2,2,2), ncol = 2), matrix(c(4,4,4,4), ncol = 2))
> z

[[1]]

     [,1] [,2]
[1,] 2 2
[2,] 2 2

[[2]]

     [,1] [,2]
[1,] 4 4
[2,] 4 4
>

I would like to calculate, for example, the mean value for each cell. I can do that the hard way as:

> (z[[1]] + z[[2]]) / 2

     [,1] [,2]
[1,] 3 3
[2,] 3 3
>

But there must be an easier way. I am also interested in other statistics (like median and sd). Since all my matrices have the same attributes (especially row and column names), I would like to preserve those in the answer.

Thanks,

Dave Kane

In case it matters:

> R.version

         _
platform i686-pc-linux-gnu

arch     i686             
os       linux-gnu        
system   i686, linux-gnu  
status                    
major    2                
minor    1.0              
year     2005             
month    04               
day      18               
language R                

>


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R-help@stat.math.ethz.ch mailing list
https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html Received on Wed May 11 00:24:56 2005

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