[GRASS-SVN] r53969 - grass-addons/grass6/raster/r.mess

[svn_grass at osgeo.org]

Author: pvanbosgeo
Date: 2012-11-22 02:29:12 -0800 (Thu, 22 Nov 2012)
New Revision: 53969

Added:
   grass-addons/grass6/raster/r.mess/description.html
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Copied: grass-addons/grass6/raster/r.mess/description.html (from rev 53960, grass-addons/grass6/raster/r.mess/r.mess.html)
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+<h2>DESCRIPTION</h2>
+
+<em>r.mess</em> computes the "Multivariate Environmental
+Similarity Surfaces" (MESS) in GRASS using R as backend. The
+MESS index was proposed by Elith et al (2010) and is also
+implemented in the Maxent software. The MESS approach
+can be described as follows (from Elith et al 2010):
+"The multivariate environmental similarity surface (MESS) calculation
+represents how similar a point is to a reference set of points, with
+respect to a set of predictor variables (V1, V2, ...). The values in
+the MESS are influenced by the full distribution of the reference points, so that
+sites within the environmental range of the reference points but in
+relatively unusual environments will have a smaller value than those in
+very common environments."
+
+<p>This module will also compute the individual environmental
+similarity surfaces (IESS), which represents how similar a point is to
+a set of reference points for each of the input variable. MESS
+is then simply calculated as the minimum of its similarity with respect
+to each variable. 
+
+<p>Any sample of interest can be used for the reference set. For example,
+it can be occurrence records for the species; a sample of a region, or a sample of
+current climate conditions in a given area. The input layer representing the
+reference distribution can be a vector point layer or a raster layer.
+
+<p>
+The IESS can have negative values – these are sites where the variable
+has a value that is outside the range in the reference set. A negative MESS
+thus represents sites where at least one variable has a value that is
+outside the range of environments over the reference set, so these are
+novel environments.
+
+<p>
+In addition to the MESS, which is the minimum(IESS), the r.mess
+function also allows to compute mean and medium of the IESS layers.
+
+<h2>NOTES</h2>
+Digits should reflect the level of precision of the input layers. I.e., if
+values of the input layers are recorded with three digits behind the comma,
+Digits should be set to 0.001 or smaller.
+
+<h2>SEE ALSO</h2>
+There is also a similar function implemented for R using the R package
+<em>raster</em>, and which is part of the dismo package in R now. See <a href="http://rossijeanpierre.wordpress.com/2012/08/13/computing-the-multivariate-environmental-similarity-surfaces-mess-index-in-r/">here</a>.
+for more information and the script.
+
+<h2>AUTHOR</h2>
+
+Contact: <a href="http://ecodiv.org/contact.html">Paulo van Breugel</a>
+
+<h2>REFERENCES</h2>
+<ul>
+<li>Elith, J., Kearney, M., & Phillips, S. 2010. The art of
+modelling range-shifting species. Methods in Ecology and Evolution 1:
+330–342.</li>
+</ul>
+
+<p>
+<i>Last changed: $Date$</i>