Hello fellow R users,
I have a matrix computation that I imagine should be relatively easy to do,
however I cannot figure out a nice way to do it. I have two matrices, for
example
mat1 <- matrix(c(1:5,rep(NA,5), 6:10), nrow=3, byrow=T)
mat2 <- matrix(c(2:6, 6:10, rep(NA,5)), nrow=3, byrow=T)
I'd like to compute the element-wise average for non-NA entries. Of course
(mat1+mat2)/2
does not work for the final two rows because of the NA's. Are there any
elegant ways to accopmlish this without writing a loop with indices?
Thanks in advance for any assistance.
Greg
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Maybe there is a more elegant solution, but here is one possibility: mat1[is.na(mat1)]<-mat2[is.na(mat1)] mat2[is.na(mat2)]<-mat1[is.na(mat2)] (mat1+mat2)/2 On Nov 21, 2007 12:30 PM, Gregory Gentlemen <gregory_gentlemen at yahoo.ca> wrote:> Hello fellow R users, > > I have a matrix computation that I imagine should be relatively easy to do, however I cannot figure out a nice way to do it. I have two matrices, for example > > mat1 <- matrix(c(1:5,rep(NA,5), 6:10), nrow=3, byrow=T) > mat2 <- matrix(c(2:6, 6:10, rep(NA,5)), nrow=3, byrow=T) > > I'd like to compute the element-wise average for non-NA entries. Of course > > (mat1+mat2)/2 > > does not work for the final two rows because of the NA's. Are there any elegant ways to accopmlish this without writing a loop with indices? > > Thanks in advance for any assistance. > > Greg > > > > --------------------------------- > > [[alternative HTML version deleted]] > > ______________________________________________ > R-help at 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. >-- Matthew C Keller Asst. Professor of Psychology University of Colorado at Boulder www.matthewckeller.com
On Wed, 2007-11-21 at 14:30 -0500, Gregory Gentlemen wrote:> Hello fellow R users, > > I have a matrix computation that I imagine should be relatively easy > to do, however I cannot figure out a nice way to do it. I have two > matrices, for example > > mat1 <- matrix(c(1:5,rep(NA,5), 6:10), nrow=3, byrow=T) > mat2 <- matrix(c(2:6, 6:10, rep(NA,5)), nrow=3, byrow=T) > > I'd like to compute the element-wise average for non-NA entries. Of > course > > (mat1+mat2)/2 > > does not work for the final two rows because of the NA's. Are there > any elegant ways to accopmlish this without writing a loop with > indices? > > Thanks in advance for any assistance. > > GregIs this what you want?> matrix(colMeans(rbind(as.vector(mat1), as.vector(mat2)),na.rm = TRUE), dim(mat1)) [,1] [,2] [,3] [,4] [,5] [1,] 1.5 2.5 3.5 4.5 5.5 [2,] 6.0 7.0 8.0 9.0 10.0 [3,] 6.0 7.0 8.0 9.0 10.0 ? HTH, Marc Schwartz