Raster comparrison
p m <stagis0 at gmail.com> writes:
Dear all, I'm looking for a test to identify significant differences (p-value) between 2 raster maps. Can you suggest me a way to solve this problem?
Hi Based on my understanding, you *can not* get a p value for the difference between two entities - to ask if the two maps are significantly different, is like asking if the two numbers 1 and two are significantly different. You can only answer that question if you know the underlying distributions and can compare these. What you can do is quantifying the difference between the two maps. One approach I used is the Earth Movers Distance, implemented in two packages: http://www.rforge.net/doc/packages/emdist/emd.html (implemented by myself and Dirk Eddelbuettel and used in some projects) and http://cran.r-project.org/web/packages/emdist/emdist.pdf by Simon Urbanek (haven't used it). But there are many other distance measures to quantify the difference between two raster maps. Which one you choose, depends on your question. Cheers, Rainer
Thank you in advance. Paul [[alternative HTML version deleted]]
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Rainer M. Krug, PhD (Conservation Ecology, SUN), MSc (Conservation Biology, UCT), Dipl. Phys. (Germany) Centre of Excellence for Invasion Biology Stellenbosch University South Africa Tel : +33 - (0)9 53 10 27 44 Cell: +33 - (0)6 85 62 59 98 Fax : +33 - (0)9 58 10 27 44 Fax (D): +49 - (0)3 21 21 25 22 44 email: Rainer at krugs.de Skype: RMkrug -------------- next part -------------- A non-text attachment was scrubbed... Name: not available Type: application/pgp-signature Size: 489 bytes Desc: not available URL: <https://stat.ethz.ch/pipermail/r-sig-geo/attachments/20130513/b898d4aa/attachment.bin>