[R] help with element-by-element sum with NA

[arun]

HI,

Try this:
A<-matrix(c(0,NA,NA,3),ncol=2)
B<-matrix(c(1,0,NA,NA),ncol=2)
 C<-matrix(c(1,1,NA,1),ncol=2)
AB<-ifelse(is.na(A),ifelse(is.na(B),NA,B), ifelse(is.na(B), A, A+B))
 ABC<-ifelse(is.na(AB),ifelse(is.na(C),NA,C),ifelse(is.na(C),AB,AB+C))
 ABC
     [,1] [,2]
[1,]    2   NA
[2,]    1    4

A.K.




----- Original Message -----
From: Thiago Couto <couto.thiagoba at gmail.com>
To: r-help at r-project.org
Cc: 
Sent: Monday, July 23, 2012 4:47 PM
Subject: [R] help with element-by-element sum with NA

Hi,

    I have three matrices which could be, for example:
    A =  0, NA
           NA, 3

    B =  1, NA
            0, NA

    C = 1, NA
            1, 1

    (The point is that they all may have NA's in some cells)

    QUESTION: How do I perform a element-by-element sum of the elements of
    these three matrices (A + B + C), ignoring NA's, to obtain:

    D = 2, NA
           1, 4

    In reality I am handling much larger matrices (not just 2x2).

    Thank you for any help!

    [[alternative HTML version deleted]]

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