Hi Mario, On Fri, Jan 28, 2011 at 12:27 PM, gaiarrido <gaiarr...@usal.es> wrote: > > Hi, > I'm trying to make a model in order to know wich factors got´s influence in > the intensity of a infection, but just in the individuals who's got this > infection. In my data I've got a variable called "prevalence" with 2 levels: > 1.- Infected individual > 0.- Non infected > > So what i'm trying to do is a subset in a model like this, > model<-aov(intensity~ageandsex*month*zone*year,subset=(prevalence=="1")) > Is a correct way?
That should work, assuming you have attached the dataframe containing the variables in your model. A safer way is to use the data agrument to aov instead: model<-aov(intensity~ageandsex*month*zone*year, data=X, subset=(prevalence=="1")) > I prefer to make the subsets with [], but doesn't work, why > >> model<-aov(hemogregarinas~edadysexo*mes*zona*ano,[prevalencia=="1"]) > Error: inesperado '[' en > "model<-aov(hemogregarinas~edadysexo*mes*zona*ano,[" > Well what is [prevalencia=="1"] indexing? Nothing, which isn't going to work. You can use model<-aov(hemogregarinas~edadysexo*mes*zona*ano, data=X[prevalencia=="1" , ]) > And finally, look at this, i don't know why I get different results >> summary(hemogregarinas[prevalencia=="1"]) > Min. 1st Qu. Median Mean 3rd Qu. Max. > 1.00 5.00 9.00 15.94 19.00 173.00 >> summary(hemogregarinas,subset=(prevalencia=="1")) > Min. 1st Qu. Median Mean 3rd Qu. Max. > 0.00 4.00 9.00 14.92 18.00 173.00 > Well I'm not sure, but I suspect it has something to do with attaching things, and getting confused about where the data is actually coming from. This gives the same results: dat <- data.frame(x=c(1,2,2,1,3,4,2,5,3,20), y = c(2,1,3,3,2,5,6,4,5,20), z=c(rep(1, 9),2)) attach(dat) summary(x[z==1]) summary(subset(x, z==1)) so again, not sure why you're getting something different. Try storing your data in a data.frame, and use the data arguments instead of attaching it, and see if you get more sensible results. Best, Ista > Thanks very much > > ----- > Mario Garrido Escudero > PhD student > Dpto. de Biología Animal, Ecología, Parasitología, Edafología y Qca. > Agrícola > Universidad de Salamanca > -- > View this message in context: > http://r.789695.n4.nabble.com/Problems-making-subsets-with-or-subset-tp3245007p3245007.html > Sent from the R help mailing list archive at Nabble.com. > > ______________________________________________ > 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. > -- Ista Zahn Graduate student University of Rochester Department of Clinical and Social Psychology http://yourpsyche.org ______________________________________________ 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.
