[GRASS-user] categories in raster map

[Moritz Lennert]

On 26/02/09 14:01, FAROUX STEPHANIE wrote:
> Moritz Lennert wrote:
>> On 26/02/09 13:34, FAROUX STEPHANIE wrote:
>>> FAROUX STEPHANIE wrote:
>>>> Moritz Lennert wrote:
>>>>> On 26/02/09 11:47, FAROUX STEPHANIE wrote:
>>>>>> Hello,
>>>>>> I see the function r.cats which allows to read categories of a 
>>>>>> raster map, but how can i define these attributes? Should i pass 
>>>>>> by a vector map? In the database menu, it doesn't seem possible to 
>>>>>> add a table for a raster map.
>>>>>
>>>>> Raster maps have categories and labels. Categories have to be 
>>>>> numerical, labels can be anything. Each pixel needs to have a 
>>>>> category value (or NULL) and optionally you can have one (and only 
>>>>> one) label per category value.
>>>>>
>>>>> BTW, r.cats is now replaced by r.category.
>>>>>
>>>>> If you want to link a cell with many attributes, you will have to 
>>>>> use vector grids (v.mkgrid or r.to.vect as you suggestà).
>>>>>
>>>>> Moritz
>>>>>
>>>> Thank you. And how do you put labels on categories please?
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>>>>
>>> I use r.reclass that's it?
>>
>> No, r.reclass "changes" category values, not labels.
>>
>> I think it would be better if you explained a bit more clearly what 
>> you want to do, i.e. what do you have and what would you like to have.
>>
>> Normally, r.category seems to be what you are looking for, using the 
>> rules= option.
>>
>> I do see that the man page might not be particularly clear on its 
>> usage (the Description part only mentions printing, not managing 
>> labels and the part on dynamic labels is a bit cryptic). But the 
>> section "Input from a file" should give you what you need.
>>
>> Moritz
>>
> Ok. I see it in the manual page of the 6.5 version.

It's been there since 6.3, which was released almost a year ago...

> Actually i work with the 6.2 version (i'm at office and i haven't 
> "control" on the installed version) and i think r.cats doesn't have this 
> option.

No.

> But with r.reclass i achieved.

Ok, you could also look at r.support for interactive editing of the labels.

> Here i have a map with integer categories values; i want to recode these 
> categories but keep old values as labels.

Depending on what you mean by recode, you could also check out r.recode.

Moritz