On May 26, 2011, at 4:22 PM, Christoph Jäckel wrote: > Hi together, > > below is a small example which produces outcome I do not understand, > namely that the median function works fine on a data.frame without > negative numbers, but doesn't work on a data.frame with one negative > number. I'm sure there is a reasonable explanation for that or better, > that I'm doing something wrong and someone could guide me how to solve > it. I tried googling it, but couldn't find a solution: > >> #Set up data frame >> df <- data.frame(V1=c(1,2,3,4),V2=c(2,3,4,5)) >> #Both work fine >> mean(df) > V1 V2 > 2.5 3.5 >> median(df) > [1] 2.5 3.5 >> >> #Now, I just make one number negative in the data.frame >> df <- data.frame(V1=c(1,2,3,-4),V2=c(2,3,4,5)) >> mean(df)#Works fine > V1 V2 > 0.5 3.5 >> median(df)#Why do I get that error? > [1] NA 0.5 > Warnmeldung: > In mean.default(X[[1L]], ...) : > argument is not numeric or logical: returning NA >> #It works fine on both columns seperately >> median(df$V1) > [1] 1.5 >> median(df$V2) > [1] 3.5
This was actually just discussed late last month. See the thread here: https://stat.ethz.ch/pipermail/r-devel/2011-April/060731.html The bottom line is that median does not have a 'method' for data frames, whereas mean does. HTH, Marc Schwartz ______________________________________________ [email protected] 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.
