Take this toy code: df <- data.frame(a=seq(10), b=rep(1:2, 5)) df.empty <- subset(df, a>10) byy <- by(data=df, INDICES=df$b, FUN=function(x) x[1,]) byy.empty <- by(data=df.empty, INDICES=df.empty$b, FUN=function(x) x[1,])
class(byy) # "by" class(byy.empty) # "by" is.list(byy) # TRUE is.list(byy.empty) # FALSE! This behavior already messed up stuff elsewhere: https://github.com/Rdatatable/data.table/issues/5258 I'd say any questions about the class of an object (whether 'class' or indirectly by 'is.**') should not have the answers depend on the specific contents of the object. Does this qualify as an R bug? Am I missing something? [[alternative HTML version deleted]] ______________________________________________ R-devel@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-devel
