Note: A new GRASS GIS stable version has been released: GRASS GIS 7.6, available here.
Updated manual page: here
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.
map1 map2
___________
0 1
0 2
1 1
1 2
2 4
map1 map2 output
____________________
0 1 1
0 2 2
1 1 3
1 2 4
2 4 5
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)
Last changed: $Date: 2016-01-28 03:21:34 -0800 (Thu, 28 Jan 2016) $
Available at: r.cross source code (history)
Note: A new GRASS GIS stable version has been released: GRASS GIS 7.6, available here.
Updated manual page: here
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© 2003-2019 GRASS Development Team, GRASS GIS 7.2.4svn Reference Manual