Clustering with ordinal data
Hello Steve,
I've been asked to help evaluate a vegetation data set, specifically to examine it for community similarity. The initial problem I see is that the data is ordinal. ? At best this only captures a relative ranking of abundance and ordinal ranks are assigned after data collection.
Just about every vegetation survey ever conducted uses either presence absence or ordinal data collection (e.g. Braun-Blanquet scores or importance scores from nested quadrats). A large number of distance metrics are in the literature to deal with such data. As well as Phil's suggestion you should definitely look at the vegan package which contains a good selection of these metrics plus numerous functions frequently used in classification and ordination of veg data. Michael
On 20 October 2010 05:14, <Steve_Friedman at nps.gov> wrote:
Hello I've been asked to help evaluate a vegetation data set, specifically to examine it for community similarity. The initial problem I see is that the data is ordinal. ? At best this only captures a relative ranking of abundance and ordinal ranks are assigned after data collection. ? ?I've been trying to find a procedure in R that can handle ordinal based classification and so far have not found one. Does one exist ? ?If there is one, which package supports this type of analysis and ?what is the function ? Thanks in advance. Steve Steve Friedman Ph. D. Spatial Statistical Analyst Everglades and Dry Tortugas National Park 950 N Krome Ave (3rd Floor) Homestead, Florida 33034 Steve_Friedman at nps.gov Office (305) 224 - 4282 Fax ? ? (305) 224 - 4147
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