R help - Jul 2012 - 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]]

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]]

______________________________________________
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.

Perhaps something like:

Reduce(function(x,y){x[is.na(x)] <- 0; y[is.na(y)] <- 0; x + y},
list(A,B,C))

Not the most elegant, but it will get the job done.

Michael

On Mon, Jul 23, 2012 at 3:47 PM, Thiago Couto <couto.thiagoba at
gmail.com> wrote:
> 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]]
>
> ______________________________________________
> 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.