-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 On 16/03/12 12:14, Andy Hartley wrote: > Dear Pascal, > > I did something similar using Mahalanobis Distance in order to assess > similarity of habitat > within protected areas to that of the surrounding
As you state, the Mahalanobis Distance measures the distance (i.e. dis-similarity) between two 2D areas - another measure for this is the earth movers distance (one package on cran, one on r-forge ( http://r-forge.r-project.org/projects/earthmovdist/ ) But I think the OP was looking fior a measure of "environmental heterogeneity", which could not be done with these distance measures easily. I would be interested in the answers. > area, in Africa. We used elevation, aridity, NDVI, NDWI, etc, so it appears > to match with your > needs. The advantage of using mahalanobis distance (as opposed to euclidean > distance) is that > it accounts for covariance between your input variables. You can read more in > our report I'll look into it, as I used the earth movers distance for a paper. Roura-Pascual, N. et al., 2010. Spatially-explicit sensitivity analysis for conservation management: exploring the influence of decisions in invasive alien plant management. Diversity and Distributions, 16, pp.426-438. Available at: http://www.sciencemag.org/content/312/5781/1715 [Accessed October 14, 2011]. If you can not get hold of the pdf, please contact me off-list. Cheers, Rainer > - http://bioval.jrc.ec.europa.eu/APAAT/AssessmentOfAfricanProtectedAreas_E > UR22780.pdf or on > the webpage - http://bioval.jrc.ec.europa.eu/APAAT/ (click a protected area > on the map, and > scroll down to the habitat irreplaceability indicator) > > Kind regards, > > Andy > - -- 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: [email protected] Skype: RMkrug -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.11 (GNU/Linux) Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org/ iEYEARECAAYFAk9jKpgACgkQoYgNqgF2ego2AQCcCiDM+ePUzjkqGuH+pAs29KK0 QkcAnRNFf6GgJctH8Q/RTWXFoAFhezh7 =VZja -----END PGP SIGNATURE----- _______________________________________________ R-sig-Geo mailing list [email protected] https://stat.ethz.ch/mailman/listinfo/r-sig-geo
