[R] matrix elementwise average with NA's

[Matthew Keller]

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