Hi,
You can also try this:
apply(simplify2array(raw),c(1,2),mean)
# [,1] [,2] [,3] [,4] [,5]
#[1,] -0.5457338 -0.2138714 -0.6555012 -0.03926681 -0.61747866
#[2,] 0.1241875 -0.5987224 -1.6752304 0.72977962 -0.47794016
#[3,] 1.0154878 -0.5175063 0.7309496 -0.57840227 0.35273184
#[4,] 0.5954131 0.8647344 -0.2717948 -0.30062601 0.73927935
#[5,] 0.4304302 0.6012879 0.1132736 0.33113125 0.23399307
#[6,] -0.7745793 1.0081508 0.3272952 0.72818327 0.07494602
A.K.
----- Original Message -----
From: "ONKELINX, Thierry" <thierry.onkel...@inbo.be>
To: "r-help@r-project.org" <r-help@r-project.org>
Cc:
Sent: Monday, November 5, 2012 5:32 AM
Subject: [R] averaging a list of matrices element wise
Dear all,
I have a list of n matrices which all have the same dimension (r x s). What
would be a fast/elegant way to calculate the element wise average? So result[1,
1] <- mean(c(raw[[1]][1, 1] , raw[[2]][1, 1], raw[[...]][1, 1], raw[[n]][1, 1]))
Here is my attempt.
#create a dummy dataset
n <- 3
r <- 5
s <- 6
raw <- lapply(seq_len(n), function(i){
matrix(rnorm(r * s), ncol = r)
})
#do the calculation
result <- array(dim = c(dim(raw[[1]]), length(raw)))
for(i in seq_along(raw)){
result[,,i] <- raw[[i]]
}
result <- apply(result, 1:2, mean)
Best regards,
Thierry
ir. Thierry Onkelinx
Instituut voor natuur- en bosonderzoek / Research Institute for Nature and
Forest
team Biometrie & Kwaliteitszorg / team Biometrics & Quality Assurance
Kliniekstraat 25
1070 Anderlecht
Belgium
+ 32 2 525 02 51
+ 32 54 43 61 85
thierry.onkel...@inbo.be
www.inbo.be
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