.TH r.regression.line 1grass "" "GRASS 6.4.4" "Grass User's Manual"
.SH NAME
\fI\fBr.regression.line\fR\fR  - Calculates linear regression from two raster maps: y = a + b*x.
.SH KEYWORDS
raster, statistics
.SH SYNOPSIS
\fBr.regression.line\fR
.br
\fBr.regression.line help\fR
.br
\fBr.regression.line\fR [\-\fBgs\fR] \fBmap1\fR=\fIname\fR \fBmap2\fR=\fIname\fR  [\fBoutput\fR=\fIname\fR]   [\-\-\fBverbose\fR]  [\-\-\fBquiet\fR] 
.SS Flags:
.IP "\fB\-g\fR" 4m
.br
Print in shell script style
.IP "\fB\-s\fR" 4m
.br
This does nothing. It is retained for backwards compatibility
.IP "\fB\-\-verbose\fR" 4m
.br
Verbose module output
.IP "\fB\-\-quiet\fR" 4m
.br
Quiet module output
.PP
.SS Parameters:
.IP "\fBmap1\fR=\fIname\fR" 4m
.br
Map for x coefficient
.IP "\fBmap2\fR=\fIname\fR" 4m
.br
Map for y coefficient
.IP "\fBoutput\fR=\fIname\fR" 4m
.br
ASCII file for storing regression coefficients (output to screen if file not specified).
.PP
.SH DESCRIPTION
\fIr.regression.line\fR 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).
.SH NOTES
The results for offset/intercept (a) and gain/slope (b) are 
identical to that obtained from R-stats's lm() function. 
.SH EXAMPLE
Comparison of the old and the new DEM in Spearfish:
\fC
.DS
.br
g.region rast=elevation.10m \-p
.br
r.regression.line map1=elevation.dem map2=elevation.10m
.br
.DE
\fR
.PP
Using the script style flag AND \fIeval\fR to make results
available in the shell:
\fC
.DS
.br
g.region rast=elevation.10m \-p
.br
eval \(gar.regression.line \-g map1=elevation.dem map2=elevation.10m\(ga
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echo $a
.br
479.615
.br
.br
echo $b
.br
0.645631
.br
.br
echo $R
.br
0.804441
.br
.DE
\fR
.SH AUTHOR
Dr. Agustin Lobo - alobo at ija.csic.es
.br
Updated to GRASS 5.7 Michael Barton, Arizona State University
.br
Script style output Markus Neteler
.br
Conversion to C module Markus Metz
.PP
\fILast changed: $Date: 2013-09-14 04:52:51 +0200 (Sat, 14 Sep 2013) $\fR
.PP
Full index
.PP
© 2003-2014 GRASS Development Team