Hi - I apologize for the 2nd post, but I think my question from a few weeks ago may have been overlooked on a Friday afternoon.
I might be missing something very obvious, but is it widely known that the aggregate function handles missing values differently depending if a data frame or a formula is the first argument ? For example, (d<- data.frame(sex=rep(0:1,each=3), wt=c(100,110,120,200,210,NA),ht=c(10,20,NA,30,40,50))) x1<- aggregate(d, by = list(d$sex), FUN = mean); names(x1)[3:4]<- c('mean.dfcl.wt','mean.dfcl.ht') x2<- aggregate(cbind(wt,ht)~sex,FUN=mean,data=d); names(x2)[2:3]<- c('mean.formcl.wt','mean.formcl.ht') cbind(x1,x2)[,c(2,3,6,4,7)] The output from the data.frame class has an NA if there are missing values in the group for the variable with missing values. But, the formula class output seems to delete the entire row (missing and non-missing values) if there are any NAs. Wouldn't one expect that the 2 forms (data frame vs formula) of aggregate would give the same result? thanks very much david freedman, atlanta -- View this message in context: http://r.789695.n4.nabble.com/data-frame-and-formula-classes-of-aggregate-tp3063668p3063668.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.