On Tue, 14 Aug 2007, Natalie O'Toole wrote: > Hi, > > Could someone please tell me how to perform a Mann-Whitney U test on a > dataset with 2 groups where one group has more data values than another? > > I have split up my 2 groups into 2 columns in my .txt file i'm using with > R. Here is the code i have so far... > > group1 <- c(LeafArea2) > group2 <- c(LeafArea1) > wilcox.test(group1, group2) > > This code works for datasets with the same number of data values in each > column, but not when there is a different number of data values in one > column than another column of data.
There is an example of that scenario on the help page for wilcox.test, so it does 'work'. What exactly went wrong for you? > Is the solution that i have to have a null value in the data column with > the fewer data values? > > I'm testing for significant diferences between the 2 groups, and the > result i'm getting in R with the uneven values is different from what i'm > getting in SPSS. We need a worked example. As the help page says, definitions do differ. If you can provide a reproducible example in R and the output from SPSS we may be able to tell you how to relate that to what you see in R. [...] > PLEASE do read the posting guide http://www.R-project.org/posting-guide.html > and provide commented, minimal, self-contained, reproducible code. As it says, we really need such code (and the output you get) to be able to help you. -- Brian D. Ripley, [EMAIL PROTECTED] Professor of Applied Statistics, http://www.stats.ox.ac.uk/~ripley/ University of Oxford, Tel: +44 1865 272861 (self) 1 South Parks Road, +44 1865 272866 (PA) Oxford OX1 3TG, UK Fax: +44 1865 272595 ______________________________________________ R-help@stat.math.ethz.ch 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.
