<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"> <html> <head> <title>GRASS GIS: r.regression.line</title> <meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1"> <link rel="stylesheet" href="grassdocs.css" type="text/css"> </head> <body bgcolor="white"> <img src="grass_logo.png" alt="GRASS logo"><hr align=center size=6 noshade> <h2>NAME</h2> <em><b>r.regression.line</b></em> - Calculates linear regression from two raster maps: y = a + b*x <h2>KEYWORDS</h2> raster, statistics <h2>SYNOPSIS</h2> <b>r.regression.line</b><br> <b>r.regression.line help</b><br> <b>r.regression.line</b> [-<b>g</b>] <b>map1</b>=<em>string</em> <b>map2</b>=<em>string</em> [<b>output</b>=<em>string</em>] [--<b>verbose</b>] [--<b>quiet</b>] <h3>Flags:</h3> <DL> <DT><b>-g</b></DT> <DD>Print in shell script style</DD> <DT><b>--verbose</b></DT> <DD>Verbose module output</DD> <DT><b>--quiet</b></DT> <DD>Quiet module output</DD> </DL> <h3>Parameters:</h3> <DL> <DT><b>map1</b>=<em>string</em></DT> <DD>Map for x coefficient</DD> <DT><b>map2</b>=<em>string</em></DT> <DD>Map for y coefficient</DD> <DT><b>output</b>=<em>string</em></DT> <DD>ASCII file for storing regression coefficients (output to screen if file not specified).</DD> </DL> <H2>DESCRIPTION</H2> <EM>r.regression.line</EM> 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), residuals (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). <br> <H2>EXAMPLE</H2> Comparison of the old and the new DEM in Spearfish: <div class="code"><pre> g.region rast=elevation.10m -p r.regression.line map1=elevation.dem map2=elevation.10m </pre></div> <p> Using the script style flag AND <em>eval</em> to make results available in the shell: <div class="code"><pre> 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 </pre></div> <H2>AUTHOR</H2> 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 <p><i>Last changed: $Date: 2007-12-17 14:53:55 +0100 (Mon, 17 Dec 2007) $</i> <HR> <P><a href="index.html">Main index</a> - <a href="raster.html">raster index</a> - <a href="full_index.html">Full index</a></P> <P>© 2003-2008 <a href="http://grass.osgeo.org">GRASS Development Team</a></p> </body> </html>
