[R] summary statistics for lists of matrices or dataframes

From: David Kane <dave_at_kanecap.com>
Date: Wed 11 May 2005 - 00:03:51 EST


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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