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r.covar(1grass) | Grass User's Manual | r.covar(1grass) |
NAME¶
r.covar - Outputs a covariance/correlation matrix for user-specified raster map layer(s).KEYWORDS¶
raster, statisticsSYNOPSIS¶
r.covarFlags:¶
- -r
-
- -q
-
- --verbose
-
- --quiet
-
Parameters:¶
- map=name[,name,...]
-
DESCRIPTION¶
r.covar outputs a covariance/correlation matrix for user-specified raster map layer(s). The output can be printed, or saved by redirecting output into a file. The output is an N x N symmetric covariance (correlation) matrix, where N is the number of raster map layers specified on the command line.NOTES¶
This module can be used as the first step of a principle components transformation. The covariance matrix would be input into a system which determines eigen values and eigen vectors. An NxN covariance matrix would result in N real eigen values and N eigen vectors (each composed of N real numbers). The module m.eigensystem in GRASS GIS Addons can be compiled and used to generate the eigen values and vectors.EXAMPLE¶
For example, r.covar map=layer.1,layer.2,layer.3 would produce a 3x3 matrix (values are example only):1.000000 0.914922 0.889581
0.914922 1.000000 0.939452
0.889581 0.939452 1.000000
1 1159.745202 < 0.691002 0.720528 0.480511 >
2 5.970541 < 0.711939 -0.635820 -0.070394 >
3 146.503197 < 0.226584 0.347470 -0.846873 >
SEE ALSO¶
i.pca, m.eigensystem, r.mapcalc, r.rescaleAUTHOR¶
Michael Shapiro, U.S. Army Construction Engineering Research Laboratory Last changed: $Date: 2014-05-02 15:52:55 +0200 (Fri, 02 May 2014) $ Full index © 2003-2014 GRASS Development TeamGRASS 6.4.4 |