[R] Adding elements in an array where I have missing data.

[John Fox]

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 at stat.math.ethz.ch 
> [mailto:r-help-bounces at 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
> 
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