On Jun 23, 2013, at 22:30 , Sarah Goslee wrote: > Hi, > > If you're doing exactly as described below, then you need to add the > data argument to wilcox.test so R knows where to find beforesmall and > aftersmall. But if so, that's a rather uninformative error message. > > Saraj
Not really, if you use the formula interface, the rhs is supposed to be the grouping, as in wilcox.test(extra ~ group, data=sleep, paired=TRUE) so it's telling you that "aftersmall" does not describe two groups. (It is unfortunate, though, that we don't have a formula interface to the parallel-vector data layout for paired tests. That is the common case, the sleep data set is a rather rare exception. A formula specification for paired columns has been talked about; something like cbind(before, after) ~ 1 should be workable, but nothing has materialized to date.) -pd > > On Sun, Jun 23, 2013 at 2:34 PM, ruth parker <parkeractonr...@gmail.com> > wrote: >> Hi, >> I've been trying to run a wilcox paired test on some data >> beforesmall aftersmall >> [1,] 63.5 512.0 >> [2,] 54.5 237.5 >> [3,] 52.5 161.5 >> [4,] 78.0 153.5 >> [5,] 53.5 68.0 >> [6,] 50.5 65.5 >> [7,] 69.0 52.0 >> [8,] 76.0 59.0 >> [9,] 68.0 66.5 >> [10,] 75.5 66.5 >> [11,] 67.0 45.5 >> [12,] 81.0 54.5 >> [13,] 49.0 44.0 >> [14,] 51.0 42.5 >> [15,] 53.0 34.5 >> >> using >> wilcox.test(beforesmall ~ aftersmall,paired=T) >> but I get the error message: >> >> Error in wilcox.test.formula(beforesmall ~ aftersmall, paired = T) : >> grouping factor must have exactly 2 levels >> >> I don't have any missing values, I have the same amount of data points for >> each group and I've looked everywhere trying to find the answer. >> Please can somebody tell me how to make it work >> thanks >> > > -- > Sarah Goslee > http://www.functionaldiversity.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. -- Peter Dalgaard, Professor, Center for Statistics, Copenhagen Business School Solbjerg Plads 3, 2000 Frederiksberg, Denmark Phone: (+45)38153501 Email: pd....@cbs.dk Priv: pda...@gmail.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.