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NAME

       r.cross  - Creates a cross product of the category values from multiple raster map layers.

KEYWORDS

       raster, statistics

SYNOPSIS

       r.cross
       r.cross --help
       r.cross  [-z]  input=string[,string,...] output=name  [--overwrite]  [--help]  [--verbose]
       [--quiet]  [--ui]

   Flags:
       -z
           Non-NULL data only

       --overwrite
           Allow output files to overwrite existing files

       --help
           Print usage summary

       --verbose
           Verbose module output

       --quiet
           Quiet module output

       --ui
           Force launching GUI dialog

   Parameters:
       input=string[,string,...] [required]
           Names of 2-30 input raster maps

       output=name [required]
           Name for output raster map

DESCRIPTION

       r.cross creates an output  raster  map  layer  representing  all  unique  combinations  of
       category values in the raster input layers (input=name,name,name, ...).  At least two, but
       not more than ten, input map layers must be specified.  The user must also specify a  name
       to be assigned to the output raster map layer created by r.cross.

OPTIONS

       The  program will be run non-interactively if the user specifies the names of between 2-10
       raster map layers be used as input, and the name of a raster map  layer  to  hold  program
       output.

       With  the  -z flag NULL values are not crossed.  This means that if a NULL value occurs in
       any input data layer, this combination is ignored,  even  if  other  data  layers  contain
       non-NULL  data.  In the example given below, use of the -z option would cause 3 categories
       to be generated instead of 5.

       If the -z flag is not specified, then map layer combinations in which some values are NULL
       will be assigned a unique category value in the resulting output map.

       Category  values  in  the  new  output map layer will be the cross-product of the category
       values from these existing input map layers.

EXAMPLE

       For example, suppose that, using two raster map layers, the following combinations occur:
                 map1   map2
                 ___________
                 NULL    1
                 NULL    2
                  1      1
                  1      2
                  2      4
       r.cross would produce a new raster map layer with 5 categories:
                 map1   map2   output
                 ____________________
                 NULL    1       0
                 NULL    2       1
                  1      1       2
                  1      2       3
                  2      4       4
       Note: The actual category value assigned to a particular combination  in  the  result  map
       layer  is  dependent  on  the order in which the combinations occur in the input map layer
       data and can be considered essentially random.  The example  given  here  is  illustrative
       only.

SUPPORT FILES

       The  category  file  created for the output raster map layer describes the combinations of
       input map layer category values which generated each category.  In the above example,  the
       category labels would be:
                 category   category
                 value      label
                 ______________________________
                    0       layer1(0) layer2(1)
                    1       layer1(0) layer2(2)
                    2       layer1(1) layer2(1)
                    3       layer1(1) layer2(2)
                    4       layer1(2) layer2(4)
       A random color table is also generated for the output map layer.

SEE ALSO

       r.covar, r.stats

AUTHOR

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

       Last changed: $Date: 2018-02-26 18:40:49 +0100 (Mon, 26 Feb 2018) $

SOURCE CODE

       Available at: r.cross source code (history)

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