Easy using rowSums :

> x <- data.frame(X1=c(0,0,1),X2=c(1,1,1),X3=c(0,1,0))

> x$Nulls <- rowSums(x==0)
> x
  X1 X2 X3 Nulls
1  0  1  0     2
2  0  1  1     1
3  1  1  0     1

Cheers


On Tue, Mar 30, 2010 at 6:31 PM, Thomas Jensen <
thomas.jensen@eup.gess.ethz.ch> wrote:

> Dear R-list,
>
> Sorry for spamming the list lately, I am just learning the more advanced
> aspects of R!
>
> I have some data that looks like this:
>
> Out Country1 Country 2 Country 3 ... CountryN
> 1       1       1       1               1
> 0       1       1       0               1
> 1       1       0       1               0
>
> I want to create a new variable that counts the number of zeros in every
> row whenever Out is equal to 1, and else it is a zero, so it would look
> like this:
>
> new_var
> 0
> 0
> 2
>
> I have tried the following:
>
> for (i in length(Out)){
> if (Out == 1) {new_var <- sum(dat[i,] != 1)}
> else {new_var <- 0}
> }
>
> but this gives me an error message.
>
> Best, Thomas
>
> ______________________________________________
> R-help@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.
>



-- 
Joris Meys
Statistical Consultant

Ghent University
Faculty of Bioscience Engineering
Department of Applied mathematics, biometrics and process control

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