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-zero 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  zero data values are not crossed.  This means that if a zero category
       value occurs in any input data layer, the combination is assigned to category zero in  the
       resulting  map  layer,  even  if  other data layers contain non-zero data.  In the example
       given above, 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  not  all  category
       values are zero will be assigned a unique category value in the resulting map layer.

       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
                 ___________
                  0      1
                  0      2
                  1      1
                  1      2
                  2      4
       r.cross would produce a new raster map layer with 5 categories:
                 map1   map2   output
                 ____________________
                  0      1       1
                  0      2       2
                  1      1       3
                  1      2       4
                  2      4       5
       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
                 ______________________________
                    1       layer1(0) layer2(1)
                    2       layer1(0) layer2(2)
                    3       layer1(1) layer2(1)
                    4       layer1(1) layer2(2)
                    5       layer1(2) layer2(4)
       A random color table is also generated for the output map layer.

NOTES

       When  run non-interactively, r.cross will not protect existing files in the user’s mapset.
       If the user specifies an output file name that already exists in his mapset, the  existing
       file will be overwritten by the new r.cross output.

SEE ALSO

       r.covar, r.stats

AUTHOR

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

       Last changed: $Date: 2011-11-08 22:24:20 +0100 (Tue, 08 Nov 2011) $

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