From: Huntsinger, Reid <reid_huntsinger_at_merck.com>

Date: Wed 11 May 2005 - 00:42:06 EST

*>
*

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

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 01:43:00 2005

Date: Wed 11 May 2005 - 00:42:06 EST

In such a situation you could make the list into a 3-way array. For example,

*> d <- dim(z[[1]]) # all the same
**> n <- length(z)
**> z <- unlist(z)
**> dim(z) <- c(d,n)
*

then you can get summary statistics for the (1,1) entries of the original z[[1]], z[[2]] etc however you would get summary statistics for the vector z[1,1,]. Moreover, you can vectorize this to get, say,

*> rowMeans(z, dims=2)
*

[,1] [,2]

[1,] 3 3

[2,] 3 3

and for arbitrary functions of the entries you can use apply():

*> apply(z, c(1,2), "median")
*

Reid Huntsinger

-----Original Message-----

From: r-help-bounces@stat.math.ethz.ch

[mailto:r-help-bounces@stat.math.ethz.ch] On Behalf Of David Kane
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:

[,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

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

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 01:43:00 2005

*
This archive was generated by hypermail 2.1.8
: Fri 03 Mar 2006 - 03:31:40 EST
*