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NAME
r.regression.line - Calculates linear regression from two raster maps: y = a + b*x.
KEYWORDS
raster, statistics
SYNOPSIS
r.regression.line
r.regression.line help
r.regression.line [-gs] map1=name map2=name [output=name] [--verbose] [--quiet]
Flags:
- -g
- Print in shell script style
- -s
- This does nothing. It is retained for backwards compatibility
- --verbose
- Verbose module output
- --quiet
- Quiet module output
Parameters:
- map1=name
- Map for x coefficient
- map2=name
- Map for y coefficient
- output=name
- ASCII file for storing regression coefficients (output to screen if file not specified).
DESCRIPTION
r.regression.line Calculates linear regression from two raster maps,
according to the formula y = a + b*x, where x and y represent raster maps.
Optionally saves regression coefficients to an ASCII file.
The result includes the following coefficients:
offset/intercept (a) and gain/slope (b), correlation coefficient (R),
number of elements (N), means (medX, medY), standard deviations
(sdX, sdY), and the F test for testing the significance of the
regression model as a whole (F).
NOTES
The results for offset/intercept (a) and gain/slope (b) are
identical to that obtained from R-stats's lm() function.
EXAMPLE
Comparison of the old and the new DEM in Spearfish:
g.region rast=elevation.10m -p
r.regression.line map1=elevation.dem map2=elevation.10m
Using the script style flag AND eval to make results
available in the shell:
g.region rast=elevation.10m -p
eval `r.regression.line -g map1=elevation.dem map2=elevation.10m`
echo $a
479.615
echo $b
0.645631
echo $R
0.804441
AUTHOR
Dr. Agustin Lobo - alobo at ija.csic.es
Updated to GRASS 5.7 Michael Barton, Arizona State University
Script style output Markus Neteler
Conversion to C module Markus Metz
Last changed: $Date: 2011-11-08 03:23:06 -0800 (Tue, 08 Nov 2011) $
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