.TH r.cross 1grass "" "GRASS 8.3.1" "GRASS GIS User's Manual"
.SH NAME
\fI\fBr.cross\fR\fR  \- Creates a cross product of the category values from multiple raster map layers.
.SH KEYWORDS
raster, statistics
.SH SYNOPSIS
\fBr.cross\fR
.br
\fBr.cross \-\-help\fR
.br
\fBr.cross\fR [\-\fBz\fR] \fBinput\fR=\fIstring\fR[,\fIstring\fR,...] \fBoutput\fR=\fIname\fR  [\-\-\fBoverwrite\fR]  [\-\-\fBhelp\fR]  [\-\-\fBverbose\fR]  [\-\-\fBquiet\fR]  [\-\-\fBui\fR]
.SS Flags:
.IP "\fB\-z\fR" 4m
.br
Non\-NULL data only
.IP "\fB\-\-overwrite\fR" 4m
.br
Allow output files to overwrite existing files
.IP "\fB\-\-help\fR" 4m
.br
Print usage summary
.IP "\fB\-\-verbose\fR" 4m
.br
Verbose module output
.IP "\fB\-\-quiet\fR" 4m
.br
Quiet module output
.IP "\fB\-\-ui\fR" 4m
.br
Force launching GUI dialog
.SS Parameters:
.IP "\fBinput\fR=\fIstring[,\fIstring\fR,...]\fR \fB[required]\fR" 4m
.br
Names of 2\-30 input raster maps
.IP "\fBoutput\fR=\fIname\fR \fB[required]\fR" 4m
.br
Name for output raster map
.SH DESCRIPTION
\fIr.cross\fR creates an \fIoutput\fR raster map layer representing
all unique combinations of category values in the raster input layers
(\fBinput=\fR\fIname,name,name\fR, ...).  At least two, but not more than
ten, \fIinput\fR map layers must be specified.  The user must also
specify a name to be assigned to the \fIoutput\fR raster map layer
created by \fIr.cross\fR.
.SH OPTIONS
The program will be run non\-interactively if the user specifies
the names of between 2\-10 raster map layers be used as \fIinput\fR,
and the name of a raster map layer to hold program \fIoutput\fR.
.PP
With the \fB\-z\fR 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 \fB\-z\fR option
would cause 3 categories to be generated instead of 5.
.PP
If the \fB\-z\fR 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.
.PP
Category values in the new \fIoutput\fR map layer will be the
cross\-product of the category values from these existing \fIinput\fR map
layers.
.SH EXAMPLE
For example, suppose that, using two raster map layers,
the following combinations occur:
.br
.nf
\fC
          map1   map2
          ___________
          NULL    1
          NULL    2
           1      1
           1      2
           2      4
\fR
.fi
\fIr.cross\fR would produce a new raster map layer with 5 categories:
.br
.nf
\fC
          map1   map2   output
          ____________________
          NULL    1       0
          NULL    2       1
           1      1       2
           1      2       3
           2      4       4
\fR
.fi
Note: The actual category value assigned to a particular combination
in the \fIresult\fR 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.
.SH SUPPORT FILES
The category file created for the \fIoutput\fR 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:
.br
.nf
\fC
          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)
\fR
.fi
A random color table is also generated for the \fIoutput\fR map layer.
.SH SEE ALSO
\fI
r.covar,
r.stats
\fR
.SH AUTHOR
Michael Shapiro, U.S. Army Construction Engineering Research Laboratory
.SH SOURCE CODE
.PP
Available at:
r.cross source code
(history)
.PP
Accessed: Sunday Dec 17 17:21:44 2023
.PP
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.PP
© 2003\-2023
GRASS Development Team,
GRASS GIS 8.3.1 Reference Manual