Dear John,

You can also get this by doing the following:

> apply(rbind(a,b), 2, sum, na.rm=T)
[1] 5 4 8

This way, you don't have to actually change the missing values to zero.
Best,
Dave.

--
Dave Armstrong
University of Maryland
Dept of Government and Politics
3140 Tydings Hall
College Park, MD 20742
Office: 2103L Cole Field House

On 5/1/06, John Fox <jfox@mcmaster.ca> wrote:
>
> Dear John,
>
> The behaviour of R is reasonable, since, in your example, 4 + NA should in
> general be NA (i.e., missing). You can do what you want by changing NAs to
> 0s:
>
> > a[is.na(a)] <- 0
> > a + b
> [1] 5 4 8
>
> I hope this helps,
> John
>
> --------------------------------
> John Fox
> Department of Sociology
> McMaster University
> Hamilton, Ontario
> Canada L8S 4M4
> 905-525-9140x23604
> http://socserv.mcmaster.ca/jfox
> --------------------------------
>
> > -----Original Message-----
> > From: r-help-bounces@stat.math.ethz.ch
> > [mailto:r-help-bounces@stat.math.ethz.ch] On Behalf Of John Kane
> > Sent: Monday, May 01, 2006 12:26 PM
> > To: R R-help
> > Subject: [R] Adding elements in an array where I have missing data.
> >
> > This is a simple question but I cannot seem to find the answer.
> > I have two vectors but with missing data and I want to add
> > them together with the NA's being ignored.
> >
> > Clearly I need to get the NA ignored.  na.action?
> >
> > I have done some searching and cannot get na.action to help.
> > This must be a common enough issue that the answer is staring
> > me in the face but I just don't see it.
> >
> > Simple example
> > a <- c(2, NA, 3)
> > b <- c(3,4, 5)
> >
> > What I want is
> > c <- a + b where
> > c  is ( 5 , 4 ,8)
> >
> > However I get
> > c is (5,NA, 8)
> >
> > What am I missing?  Or do I somehow need to recode the NA's
> > as missing?
> >
> > Thanks
> >
> > ______________________________________________
> > R-help@stat.math.ethz.ch mailing list
> > https://stat.ethz.ch/mailman/listinfo/r-help
> > PLEASE do read the posting guide!
> > http://www.R-project.org/posting-guide.html
>
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