Well, you're rather stuck writing them all out unless you have them in some other data structure.
## three dimensional array (50 4 x 4 matrices) x <- array(rnorm(16 * 50), dim = c(4, 4, 50)) > apply(x, 1:2, mean) [,1] [,2] [,3] [,4] [1,] -0.09460574 0.01572077 -0.166194625 -0.28176540 [2,] -0.26649044 -0.23546332 -0.003559647 -0.09857819 [3,] 0.12657883 0.10979631 0.368414189 -0.13653997 [4,] -0.02827496 0.07634844 -0.088057890 0.06208034 ## list of length 50 each element is 4 x 4 matrix > y <- rep(list(matrix(rnorm(16), 4, 4)), 50) > length(y) [1] 50 > Reduce(`+`, y)/length(y) [,1] [,2] [,3] [,4] [1,] -1.8334660 0.67812999 0.20159314 1.6163501 [2,] -0.6716821 -0.23942474 -0.50482638 -0.5765309 [3,] 0.7991496 0.38674047 -0.02128386 -1.1868209 [4,] -1.1654429 0.06773386 0.13538268 0.3847375 See ?array ?apply ?Reduce for documentation Hope this helps, Josh On Wed, Nov 30, 2011 at 7:22 PM, T.D. Rudolph <tylerdrudo...@gmail.com> wrote: > > What if you have over 50 matrices and you don't want to write them all out > one-by-one? I know there's something really quite simple, but I haven't > found it yet!... > > -- > View this message in context: > http://r.789695.n4.nabble.com/Average-of-Two-Matrices-tp860672p4126615.html > Sent from the R help mailing list archive at Nabble.com. > > ______________________________________________ > R-help@r-project.org mailing list > https://stat.ethz.ch/mailman/listinfo/r-help > PLEASE do read the posting guide http://www.R-project.org/posting-guide.html > and provide commented, minimal, self-contained, reproducible code. -- Joshua Wiley Ph.D. Student, Health Psychology Programmer Analyst II, ATS Statistical Consulting Group University of California, Los Angeles https://joshuawiley.com/ ______________________________________________ R-help@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.