On Tue, 30 Jul 2002, Santiago Saura Martínez de Toda wrote: > Dear list members, > I have calculated the shared edges existing between each of the > cover types (nine in this particular case) of a vector map. > My objective is to determine, on the basis of this shared-edge analysis, > which cover types tend to be associated (adjacent/contiguous/next)to each > other. > A simple table with the length of the shared edges for each two > cover types is not too meaningful. For example, one of the cover types > occupies about 70% of total landscape area, and thus the other cover > types tend to share most of their edges with this dominant type. This > (total edge shared) does not imply that there is a significant > association (tendency for being located adjacent in the landscape). I > tried to obtain a simple association measure that considered (corrected > for) the effect of the different abundance of each of the cover types, > but I don't feel really confident with the results I got. > I wonder if there is available any association index or statistical test > that determines whether a positive, negative or non-significant association > exists between two given cover types in the landscape (preferably as derived > from shared edges information). I guess this may be simpler to answer in > raster than in vector spatial data.
Maybe a join count test, perhaps using the shared boundary length in the weights matrix - Cliff, A. D., Ord, J. K. 1981 Spatial processes, Pion, p. 20. There is a version of the same colours (BB) test for R (www.r-project.org) in the contributed package "spdep", and SpaceStat (www.spacestat.com) also does it. Roger -- Roger Bivand Economic Geography Section, Department of Economics, Norwegian School of Economics and Business Administration, Breiviksveien 40, N-5045 Bergen, Norway. voice: +47 55 95 93 55; fax +47 55 95 93 93 e-mail: [EMAIL PROTECTED] and: Department of Geography and Regional Development, University of Gdansk, al. Mar. J. Pilsudskiego 46, PL-81 378 Gdynia, Poland. -- * To post a message to the list, send it to [EMAIL PROTECTED] * As a general service to the users, please remember to post a summary of any useful responses to your questions. * To unsubscribe, send an email to [EMAIL PROTECTED] with no subject and "unsubscribe ai-geostats" followed by "end" on the next line in the message body. DO NOT SEND Subscribe/Unsubscribe requests to the list * Support to the list is provided at http://www.ai-geostats.org
