  Hi,

Not sure since I've never done it, but shouldn't it be NA instead of NULL?

Ivan

Le 9/17/2010 15:23, n.vialma@libero.it a écrit :
> Dear list,
> I have a question I'm trying to use the following command in R, but it gives
> me an error message.The command is:
>
> data<-ddply(data,c("year","name"), transform, check1=ifelse(check1==1&
> check2==1, 1,NULL))
>
> so in my data frame I already have the check1 variable, if the conditions
> (check1==1&  check2==1) is respected, check has to have 1 as value, whereas if
> it is not I want that variable to maintain its value.
> Anyone knows, how to do this, by doing this for name and year??
>
> ______________________________________________
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> 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.
>

-- 
Ivan CALANDRA
PhD Student
University of Hamburg
Biozentrum Grindel und Zoologisches Museum
Abt. Säugetiere
Martin-Luther-King-Platz 3
D-20146 Hamburg, GERMANY
+49(0)40 42838 6231
ivan.calandra@uni-hamburg.de

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