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

SOURCE CODE

       Available at: r.cross source code (history)

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       © 2003-2019 GRASS Development Team, GRASS GIS 7.8.2 Reference Manual