NAME
r.cross - Creates a cross product of the category values from
multiple raster map layers.
(GRASS Raster Program)
SYNOPSIS
r.cross
r.cross help
r.cross [-qz]
input=name,name[,name,...] output=name
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,
using the form:
-
r.cross [-qz]
input=name,name[,name,...] output=name
where each input name specifies the name of a raster map layer to
be used in calculating the cross product, the output name
specifies the name of a raster map layer to hold program output,
and the options -q and -z respectively specify that the program
is to run quietly and exclude zero data values.
Alternately, the user can simply type r.cross on the command line,
without program arguments. In this case, the user will be prompted for
needed input and output map names and flag settings
using the standard GRASS parser interface.
Flags:
- -q
- Run quietly. Supresses output of program percent-complete messages.
If this flag is not used, these messages are printed out.
- -z
- Do not cross zero data values.
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.
Parameters:
- input=name,name[,name,...]
- The names of between two and ten existing raster map layers
to be used as input.
Category values in the new output map layer will
be the cross-product of
the category values from these existing input map layers.
- output=name
- The name assigned to the new raster map layer created by
r.cross,
containing program output.
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
parser
AUTHOR
Michael Shapiro, U.S. Army Construction Engineering
Research Laboratory