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@@ -17,18 +17,27 @@ eigen values and eigen vectors. An NxN covariance matrix would result in
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N real eigen values and N eigen vectors (each composed of N real numbers).
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<p>
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-The module <em><a href="http://grasswiki.osgeo.org/wiki/AddOns/GRASS_6#m.eigensystem">m.eigensystem</a></em>
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+The module <em><a href="http://grasswiki.osgeo.org/wiki/AddOns/GRASS_7/misc#m.eigensystem">m.eigensystem</a></em>
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in <a href="http://grass.osgeo.org/download/addons/">GRASS GIS Addons</a>
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can be compiled and used to generate the eigen values and vectors.
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<h2>EXAMPLE</h2>
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+<!--
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+For example (North Carolina sample dataset),
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+
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+<div class="code"><pre>
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+g.region raster=elev_ned_30m -p
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+r.covar -r map=elevation,elev_ned_30m,elev_srtm_30m
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+</pre></div>
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+-->
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+
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For example,
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-<dl>
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-<dd>
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-<b>r.covar</b> map=<em>layer.1</em>,<em>layer.2</em>,<em>layer.3</em>
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-</dl>
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+<div class="code"><pre>
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+g.region raster=layer.1 -p
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+r.covar -r map=layer.1,layer.2,layer.3
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+</pre></div>
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would produce a 3x3 matrix (values are example only):
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@@ -43,23 +52,20 @@ for the covariance matrix are:
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<div class="code"><pre>
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component eigen value eigen vector
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- 1 1159.745202 < 0.691002 0.720528 0.480511 >
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- 2 5.970541 < 0.711939 -0.635820 -0.070394 >
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- 3 146.503197 < 0.226584 0.347470 -0.846873 >
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+ 1 1159.745202 <0.691002 0.720528 0.480511>
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+ 2 5.970541 <0.711939 -0.635820 -0.070394>
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+ 3 146.503197 <0.226584 0.347470 -0.846873>
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</pre></div>
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The component corresponding to each vector can be produced using
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<em><a href="r.mapcalc.html">r.mapcalc</a></em>
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as follows:
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-<dl>
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-<dd>
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-<b>r.mapcalc</b> 'pc.1 = 0.691002*layer.1 + 0.720528*layer.2 + 0.480511*layer.3'
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-<br>
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-<b>r.mapcalc</b> 'pc.2 = 0.711939*layer.1 - 0.635820*layer.2 - 0.070394*layer.3'
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-<br>
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-<b>r.mapcalc</b> 'pc.3 = 0.226584*layer.1 + 0.347470*layer.2 - 0.846873*layer.3'
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-</dl>
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+<div class="code"><pre>
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+r.mapcalc "pc.1 = 0.691002*layer.1 + 0.720528*layer.2 + 0.480511*layer.3"
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+r.mapcalc "pc.2 = 0.711939*layer.1 - 0.635820*layer.2 - 0.070394*layer.3"
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+r.mapcalc "pc.3 = 0.226584*layer.1 + 0.347470*layer.2 - 0.846873*layer.3"
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+</pre></div>
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Note that based on the relative sizes of the eigen values,
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<em>pc.1</em>
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@@ -80,10 +86,12 @@ This can be done with <em><a href="r.rescale.html">r.rescale</a></em>.
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<h2>SEE ALSO</h2>
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-<em><a href="i.pca.html">i.pca</a></em>,
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-<em><a href="m.eigensystem.html">m.eigensystem</a></em>,
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-<em><a href="r.mapcalc.html">r.mapcalc</a></em>,
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-<em><a href="r.rescale.html">r.rescale</a></em>
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+<em>
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+<a href="i.pca.html">i.pca</a>,
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+<a href="m.eigensystem.html">m.eigensystem</a> (Addon),
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+<a href="r.mapcalc.html">r.mapcalc</a>,
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+<a href="r.rescale.html">r.rescale</a>
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+</em>
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<h2>AUTHOR</h2>
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