You need to ask yourself a number of questions, e.g. What is the hypothesis you wish to test? What is the test statistic you wish to use to test it? How can I get some information on where my value of that statistic sits with respect to its null hypothesis distribution?
p-values do not exist independently of hypothesis tests. (It would also be a coutresy to the list to give your name and affiliation, as the posting guide suggests.) Bill Venables CSIRO Laboratories PO Box 120, Cleveland, 4163 AUSTRALIA Office Phone (email preferred): +61 7 3826 7251 Fax (if absolutely necessary): +61 7 3826 7304 Mobile: +61 4 8819 4402 Home Phone: +61 7 3286 7700 mailto:[EMAIL PROTECTED] http://www.cmis.csiro.au/bill.venables/ -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Michael Denslow Sent: Saturday, 5 July 2008 2:14 PM To: r-help@r-project.org Subject: [R] p-value for Nonmetric Multidimentional Scaling? Dear R-helpers, I am running metaMDS in the vegan package, which uses isoMDS in MASS, to perform Nonmetric Multidimentional Scaling (NMDS). I have seen some authors report a p-value for the NMDS ordination based on randomization of the dataset. As I understand it this is meant to compare the stress in your dataset to multiple runs of randomized data. I do not see a way to perform such a test in vegan or MASS. So my questions are: Is this necessary? and Does R have a function to do this? Thanks in advance for your help, Michael ______________________________________________ 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. ______________________________________________ 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.
