<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"> <html> <head> <title>GRASS GIS: r.median</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.median</b></em> - Finds the median of values in a cover map within areas assigned the same category value in a user-specified base map. <h2>KEYWORDS</h2> raster <h2>SYNOPSIS</h2> <b>r.median</b><br> <b>r.median help</b><br> <b>r.median</b> <b>base</b>=<em>name</em> <b>cover</b>=<em>name</em> <b>output</b>=<em>name</em> [--<b>overwrite</b>] [--<b>verbose</b>] [--<b>quiet</b>] <h3>Flags:</h3> <DL> <DT><b>--overwrite</b></DT> <DD>Allow output files to overwrite existing files</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>base</b>=<em>name</em></DT> <DD>Name of base raster map</DD> <DT><b>cover</b>=<em>name</em></DT> <DD>Name of cover raster map</DD> <DT><b>output</b>=<em>name</em></DT> <DD>Name for output raster map</DD> </DL> <H2>DESCRIPTION</H2> <EM>r.median</EM> calculates the median category of data contained in a <B>cover</B> raster map layer for areas assigned the same category value in the user-specified <B>base</B> raster map layer. These median values are stored in the new <B>output</B> map layer. <P> The <B>output</B> map is actually a <EM>reclass</EM> of the <B>base</B> map. The <B>base</B> map is an existing raster map layer in the user's current mapset search path. For each group of cells assigned the same category value in the <B>base</B> map, the median of the values assigned these cells in the <B>cover</B> map will be computed. <P> The <B>cover</B> map is an existing raster map layer containing the values to be used to compute the median within each category of the <B>base</B> map. <H2>NOTES</H2> The user should use the results of <EM>r.median</EM> with care. Since this utility assigns a value to each cell which is based on global information (i.e., information at spatial locations other than just the location of the cell itself), the resultant map layer is only valid if the geographic region and mask settings are the same as they were at the time that the result map was created. <P> Results are affected by the current region settings and mask. <H2>EXAMPLE</H2> Median K-factor (erosion) for Spearfish fields: <div class="code"><pre> g.region rast=fields -p r.median base=fields cover=soils.Kfactor output=K.by.farm.median r.univar K.by.farm.median </pre></div> <H2>SEE ALSO</H2> <EM><A HREF="g.region.html">g.region</A></EM>, <EM><A HREF="r.average.html">r.average</A></EM>, <EM><A HREF="r.category.html">r.category</A></EM>, <EM><A HREF="r.clump.html">r.clump</A></EM>, <EM><A HREF="r.describe.html">r.describe</A></EM>, <EM><A HREF="r.mapcalc.html">r.mapcalc</A></EM>, <EM><A HREF="r.mfilter.html">r.mfilter</A></EM>, <EM><A HREF="r.mode.html">r.mode</A></EM>, <EM><A HREF="r.neighbors.html">r.neighbors</A></EM>, <EM><A HREF="r.reclass.html">r.reclass</A></EM>, <EM><A HREF="r.statistics.html">r.statistics</A></EM>, <EM><A HREF="r.stats.html">r.stats</A></EM>, <EM><A HREF="r.univar.html">r.univar</A></EM> <H2>AUTHOR</H2> Michael Shapiro, U.S.Army Construction Engineering Research Laboratory <p><i>Last changed: $Date: 2007-10-10 10:01:00 +0200 (Wed, 10 Oct 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>
