NAME

       r.median   -  Finds  the  median  of  values in a cover map within areas assigned the same
       category value in a user-specified base map.

KEYWORDS

       raster, statistics

SYNOPSIS

       r.median
       r.median help
       r.median base=name cover=name output=name  [--overwrite]  [--verbose]  [--quiet]

   Flags:
       --overwrite
           Allow output files to overwrite existing files

       --verbose
           Verbose module output

       --quiet
           Quiet module output

   Parameters:
       base=name
           Name of base raster map

       cover=name
           Name of cover raster map

       output=name
           Name for output raster map

DESCRIPTION

       r.median calculates the median category of data contained in a cover raster map layer  for
       areas assigned the same category value in the user-specified base raster map layer.  These
       median values are stored in the new output map layer.

       The output map is actually a reclass of the base map.  The base  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 base map, the median of the values assigned these cells in  the
       cover map will be computed.

       The  cover map is an existing raster map layer containing the values to be used to compute
       the median within each category of the base map.

NOTES

       The user should use the results of r.median 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.

       Results are affected by the current region settings and mask.

EXAMPLE

       Median K-factor (erosion) for Spearfish fields:
       g.region rast=fields -p
       r.median base=fields cover=soils.Kfactor output=K.by.farm.median
       r.univar K.by.farm.median

SEE ALSO

       g.region,  r.average,  r.category,  r.clump,  r.describe,  r.mapcalc,  r.mfilter,  r.mode,
       r.neighbors, r.reclass, r.statistics, r.stats, r.univar

AUTHOR

       Michael Shapiro, U.S.Army Construction Engineering Research Laboratory

       Last changed: $Date: 2008-05-16 12:09:06 -0700 (Fri, 16 May 2008) $

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       © 2003-2013 GRASS Development Team