[R] Fwd: Sum of a couple of variables of which a few have NA values

[Ivan Calandra]

Dear Petra,

I think the easiest way, because the most flexible to me, would be to 
have an object containing the indexes of the variables you want to use.

indx <- c(2,3,4,6,35)  # The first column is "id" right?
dat$sums <- rowSums(dat[indx], na.rm=TRUE)

See what I mean?
There are probably other solutions, but this is what I would do.
HTH,
Ivan



Le 10/01/12 19:47, PetraOpic a écrit :
> Dear Ivan,
>
> Thank you very much for your help.
>
> How do I use rowSums if I need to "skip" a variable from summing? (example:
> sum var1, var2, var3, var5, var34 only).
>
> Thanks in advance,
> Petra Opic
>
> --
> View this message in context: http://r.789695.n4.nabble.com/Sum-of-a-couple-of-variables-of-which-a-few-have-NA-values-tp4282448p4282969.html
> Sent from the R help mailing list archive at Nabble.com.
>
> ______________________________________________
> R-help at r-project.org mailing list
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>
>


-------- Message original --------
Sujet: 	Fwd: [R] Sum of a couple of variables of which a few have NA values
Date : 	Tue, 10 Jan 2012 17:44:44 +0100
De : 	Ivan Calandra <ivan.calandra at u-bourgogne.fr>
Répondre à : 	ivan.calandra at u-bourgogne.fr
Pour : 	R list <r-help at r-project.org>



Hi Petra,

Try this:
dat$sums<- rowSums(dat[3:5], na.rm=TRUE)

I think this should do what you're looking for
HTH,
Ivan

-------- Message original --------
Sujet: 	[R] Sum of a couple of variables of which a few have NA values
Date : 	Tue, 10 Jan 2012 17:25:21 +0100
De : 	Petra Opic<petraopic at gmail.com>
Pour : 	r-help at r-project.org



Dear everyone,

I have looked all over the internet but I cannot find a way to solve my problem.

In my data I want to sum a couple of variables. Some of these
variables have NA values, and when I add them together, the result is
NA

dat<- data.frame(
id = gl(5,1),
var1 = rnorm(5, 10),
var2 = rnorm(5, 7),
var3 = rnorm(5, 6),
var4 = rnorm(5, 3),
var5 = rnorm(5, 8)
)
dat[3,3]<- NA
dat[4,5]<- NA

>   dat
  id      var1     var2     var3     var4     var5
1  1  9.371328 7.830814 5.032541 3.491053 7.626418
2  2 10.413516 7.333630 6.557178 1.465597 8.591770
3  3 10.967073       NA 6.674079 3.946451 7.251263
4  4  9.900380 7.727111 5.059698       NA 6.632962
5  5  9.191068 7.901271 6.652410 2.734856 8.484757

attach(dat)

dat$sum<- var2 + var3 + var4 # I think I'm doing this wrong, but I
don't know what command to use

>   dat
   id      var1     var2     var3     var4     var5      sum
1  1  9.371328 7.830814 5.032541 3.491053 7.626418 16.35441
2  2 10.413516 7.333630 6.557178 1.465597 8.591770 15.35640
3  3 10.967073       NA 6.674079 3.946451 7.251263       NA
4  4  9.900380 7.727111 5.059698       NA 6.632962       NA
5  5  9.191068 7.901271 6.652410 2.734856 8.484757 17.28854

I would like to omit the values of NA and just sum the rest.

I tried to use rowSums() but that sums an entire row and I only need a
few variables.

Does anyone know how to do this?

Thanks in advance,
Petra

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PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.




-- 
Ivan CALANDRA
Université de Bourgogne
UMR CNRS 5561 Biogéosciences
6 Boulevard Gabriel
21000 Dijon, FRANCE
ivan.calandra at u-bourgogne.fr