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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