---
name: "r.cross"
section: "1grass"
platform: "linux"
package: "grass-doc"
version: "8.4.1-1"
release: "Debian 13 (Trixie)"
platforms: ["linux"]
url: "https://new.carta.tech/r.cross"
---

# r.cross(1grass)

Creates a cross product of the category values from multiple raster map layers.

## 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 30, *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

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)

Accessed: Monday Feb 24 17:50:35 2025

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