Hi Dave,
maybe you can find these functions useful:
matSums <- function(lis){
out <- array(data=0., dim=dim(lis[[1]]))
for(i in seq(along=lis)) out <- out + lis[[i]]
out
}
##
matMeans <- function(lis) matSums(lis) / length(lis)
##
matFun <- function(lis, FUN, ...){
if(!is.list(lis) || !all(sapply(lis, is.matrix))) stop("'lis' must
be a list containing 2-dimensional arrays")
dims <- sapply(lis, dim)
n <- dims[1, 1]
p <- dims[2, 1]
if(!all(n==dims[1,]) || !all(p==dims[2,])) stop("the matrices must
have the same dimensions")
out <- apply(matrix(unlist(lis), n * p, length(lis)), 1, FUN, ...)
dim(out) <- c(n, p)
out
}
# The first two are faster than "matFun(lis, sum)" or "matFun(lis,
mean)"
# for large and many matrices
#############
matFun <- function(lis, FUN, ...){
if(!is.list(lis) || !all(sapply(lis, is.matrix))) stop("'lis' must
be a list containing 2-dimensional arrays")
dims <- sapply(lis, dim)
n <- dims[1, 1]
p <- dims[2, 1]
if(!all(n==dims[1,]) || !all(p==dims[2,])) stop("the matrices must
have the same dimensions")
out <- apply(matrix(unlist(lis), n*p, length(lis)), 1, FUN, ...)
dim(out) <- c(n, p)
out
}
###########
lis <- list(matrix(c(2,2,2,2), ncol = 2), matrix(c(4,4,4,4), ncol =
2), matrix(c(5,5,5,5), ncol=2))
matSums(lis)
matFun(lis, sum)
matMeans(lis)
matFun(lis, mean)
matFun(lis, median)
matFun(lis, sd)
Best,
Dimitris
----
Dimitris Rizopoulos
Ph.D. Student
Biostatistical Centre
School of Public Health
Catholic University of Leuven
Address: Kapucijnenvoer 35, Leuven, Belgium
Tel: +32/16/336899
Fax: +32/16/337015
Web: http://www.med.kuleuven.ac.be/biostat/http://www.student.kuleuven.ac.be/~m0390867/dimitris.htm
----- Original Message -----
From: "David Kane" <dave at kanecap.com>
To: <r-help at stat.math.ethz.ch>
Sent: Tuesday, May 10, 2005 4:03 PM
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
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