summary statistics for lists of matrices or dataframes

You could use 'do.call' with 'bind.array' (from S Poetry) or 'abind'
to convert your list of matrices into a three-dimensional array.

Patrick Burns

Burns Statistics
patrick at burns-stat.com
+44 (0)20 8525 0696
http://www.burns-stat.com
(home of S Poetry and "A Guide for the Unwilling S User")

David Kane wrote:

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