## 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.
The flag *-s* is inactive as always high precision is
calculated (kept for backward compatibility).

## 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: $Date$*