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 4r.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 5Note: 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.
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.
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