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: 2013-09-14 04:52:51 +0200 (Sat, 14 Sep 2013) $ Full index © 2003-2014 GRASS Development Team