[GRASS-user] r.cross doesn't work correctly.

[Nikos Alexandris]

* Markus Metz <markus.metz.giswork at gmail.com> [2018-02-26 13:01:35 +0100]:

>On Mon, Feb 26, 2018 at 11:19 AM, Gra <graziaz at gmail.com> wrote:
>>
>> Dear community
>>
>> I use r.cross to combine and then reclassify a set of indicators.
>>
>> I realised that r.cross doesn't work correctly.
>>
>> I have two inputs maps with values from 1 to 3 each.
>>
>>
>> the problem is that r.category doesn't list the first combination (eg 1
>to 1)
>>
>> eg
>> r.category map=myinput at in_data
>
>> 0
>> 1 category 1; category 2
>> 2 category 1; category 3
>> 3 category 2; category 1
>> 4 category 2; category 2
>> 5 category 2; category 3
>> 6 category 3; category 1
>> 7 category 3; category 2
>> 8 category 3; category 3
>>
>> in reality the first combination exists (0 is empty but  I should have
>there category 1; category 1)
>> the problem is that I have to iterate on 700 cases and I wont check and
>correct manually.
>>
>> could  you fix it?
>
>Please try trunk r72281

Works for me, thank you.

I get now (compared to what I've posted in the other post):

0       CZfg; category 1
1       CZfg; category 2
2       CZbg; category 1
3       CZbg; category 2
4       CZg; category 1

What about the -z flag, though?

r.category geology_Test
217     CZfg
405     CZbg
766     CZg

r.category basins_0_12
0       0
12      Twelve

r.cross input=geology_Test,basins_0_12 out=cross_Test_6
r.cross input=geology_Test,basins_0_12 out=cross_Test_7 -z

r.category cross_Test_6
0       CZfg; 0
1       CZfg; Twelve
2       CZbg; 0
3       CZbg; Twelve
4       CZg; 0

and

r.category cross_Test_7
0       CZfg; 0
1       CZfg; Twelve
2       CZbg; 0
3       CZbg; Twelve
4       CZg; 0


The manual reads:

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.

By the way, it should be: "In the following example..." and not "In the
example given above...".

Nikos


>Markus M
>
>> thanks
>> Grazia
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