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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