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 [-zq] input=string[,string,...] output=name  [--overwrite]  [--verbose]  [--quiet]

   Flags:
       -z
           Non-zero data only

       -q
           Run quietly

       --overwrite
           Allow output files to overwrite existing files

       --verbose
           Verbose module output

       --quiet
           Quiet module output

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

       output=name
           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: 2008-08-11 20:34:28 -0700 (Mon, 11 Aug 2008) $

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