R help - May 2006 - 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

On Mon, 2006-05-01 at 13:26 -0400, John Kane wrote:
> 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
Your example shows that you are not ignoring the NA's but treating them
as zeroes. This may or may not make sense depending on the application.

Your comment "Or do I somehow need to recode the NA's as missing"
is
puzzling. NA denotes a missing value.

If you insist on treating NA's as zeroes, then just replace the NA's
with zeroes before adding:
> a[is.na(a)] <- 0
Rick B.

> 
> ______________________________________________
> R-help at 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
-- 
Assistant Professor
University of Pittsburgh School of Medicine
Department of Ophthalmology
412 648 9138
BST S 207

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
> 
> ______________________________________________
> R-help at 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

Here are a few alternatives:

replace(a, is.na(a), 0) + b

ifelse(is.na(a), 0, a) + b

mapply(sum, a, b, MoreArgs = list(na.rm = TRUE))

On 5/1/06, John Kane <jrkrideau at yahoo.ca>
wrote:
> 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 at 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
>

> 
> Here are a few alternatives:
> 
> replace(a, is.na(a), 0) + b
> 
> ifelse(is.na(a), 0, a) + b
> 
> mapply(sum, a, b, MoreArgs = list(na.rm = TRUE))
> 
Well, Gabor, if you want to get fancy...

evalq({a[is.na(a)]<-0;a})+b

(and variants...)

Cheers,
Bert

On 5/2/06, Berton Gunter <gunter.berton at gene.com>
wrote:
> >
> > Here are a few alternatives:
> >
> > replace(a, is.na(a), 0) + b
> >
> > ifelse(is.na(a), 0, a) + b
> >
> > mapply(sum, a, b, MoreArgs = list(na.rm = TRUE))
> >
>
> Well, Gabor, if you want to get fancy...
>
> evalq({a[is.na(a)]<-0;a})+b
>
Note that the evalq can be omitted:

   { a[is.na] <- 0; a } + b