Provided by: grass-doc_6.4.3-3_all

**NAME**

r.regression.line- Calculates linear regression from two raster maps: y = a + b*x.

**KEYWORDS**

raster, statistics

**SYNOPSIS**

r.regression.liner.regression.linehelpr.regression.line[-gs]map1=namemap2=name[output=name] [--verbose] [--quiet]Flags:-gPrint in shell script style-sSlower but accurate (applies to FP maps only--verboseVerbose module output--quietQuiet module outputParameters:map1=nameMap for x coefficientmap2=nameMap for y coefficientoutput=nameASCII file for storing regression coefficients (output to screen if file not specified).

**DESCRIPTION**

r.regression.lineCalculates 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-sis 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 ANDevalto 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 MetzLastchanged:$Date:2011-11-0803:29:50-0800(Tue,08Nov2011)$Full index © 2003-2013 GRASS Development Team