[R] Combine two matricies

[Dimitris Rizopoulos]

try this:

a <- matrix(c(3,4,5,2,3,4,1,1,2), nrow=3, ncol=3)
x <- matrix(c(3, NA, NA, NA, 2, 5, NA, 2, 2), nrow=3, ncol=3)

ind <- is.na(x)
x[ind] <- a[ind]
x


I hope it helps.

Best,
Dimitris


Tom Liptrot wrote:
> Hi,
> 
> I have two matricies a and x:
> 
> a<-matrix(c(3,4,5,2,3,4,1,1,2), nrow=3, ncol=3)
> 
>  [,1] [,2] [,3]
> [1,]    3    2    1
> [2,]    4    3    1
> [3,]    5    4    2
> 
> x<-matrix(c(3, NA, NA, NA, 2, 5, NA, 2, 2), nrow=3, ncol=3)
> 
>  [,1] [,2] [,3]
> [1,]    3   NA   NA
> [2,]   NA    2    2
> [3,]   NA    5    2
> 
> I wish to combine these two into one matrix using the values from x where x has values, and values from a where x has NA's, giving a new matrix which would look like this:
> 
> ax<-matrix(c(3,4,5,2,2,5,1,2,2), nrow=3, ncol=3)
> 
>     [,1] [,2] [,3]
> [1,]    3    2    1
> [2,]    4    2    2
> [3,]    5    5    2
> 
> I want an automatic way of doing this as my actual application is a much larger matrix.
> 
> Thanks in advance
> 
> Tom
> 
> 
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-- 
Dimitris Rizopoulos
Assistant Professor
Department of Biostatistics
Erasmus University Medical Center

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