Problems making subsets with [] or "subset"
Hi Mario,
On Fri, Jan 28, 2011 at 12:27 PM, gaiarrido <gaiarrido at 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 Biolog?a Animal, Ecolog?a, Parasitolog?a, Edafolog?a y Qca. Agr?cola 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.
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Ista Zahn Graduate student University of Rochester Department of Clinical and Social Psychology http://yourpsyche.org