Hello, I can't have different data these data came from mice that have lived under certain condition in the lab! I have just read the mentioned publication "Should the median test be retired from general use?" It says in the conclusion "If one felt that the data could not come from a Cauchy or slash distribution, the Wilcoxon should be used."! What is this? Is there is any test in R for a Cauchy or slash distribution? Can I used the unpaired Wilcoxon, or I have a Cauchy distributed data?
Many thanks, Linda 2010/5/27 Joshua Wiley <jwiley.ps...@gmail.com> > Hello Linda, > > The "problem" is actually the median of your data. What the function > median.test() does first is combine both groups. Look at this: > > median(c(group1, group2)) > > the median is 1, but the lowest value of the groups is also 1. So > when the function does the logical check z < m where z = c(group1, > group2) and m is the median, there are no values that are less than > the median value. Therefore there is only 1 level, and the fisher > test fails. > > You would either need different data or adjust the function to be: > > fisher.test(z <= m, g)$p.value > > that way it's less than or equal to the median. > > Hope that helps, > > Josh > > On Thu, May 27, 2010 at 7:24 AM, linda Porz <linda.p...@gmail.com> wrote: > > Hi all, > > > > I have found the following function online > > > > median.test<-function(y1,y2){ > > z<-c(y1,y2) > > g <- rep(1:2, c(length(y1),length(y2))) > > m<-median(z) > > fisher.test(z<m,g)$p.value > > } > > > > in > > > > http://www.mail-archive.com/r-help@r-project.org/msg95278.html > > > > I have the following data > > > >> group1 <- c(2, 2, 2, 1, 4, 3, 1, 1) > >> group2 <- c(3, 1, 3, 1, 4, 1, 1, 1, 7, 1, 1, 1, 1, 1, 2) > >> median.test(w1,group1) > > [1] 1 > >> median.test(group1,group2) > > Error in fisher.test(z < m, g) : 'x' and 'y' must have at least 2 levels > > > > I am very thankful in advance for any suggestion and help. > > > > Regards, > > Linda > > > > [[alternative HTML version deleted]] > > > > ______________________________________________ > > 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. > > > > > > -- > Joshua Wiley > Senior in Psychology > University of California, Riverside > http://www.joshuawiley.com/ > [[alternative HTML version deleted]] ______________________________________________ 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.