[GRASS-user] Exporting labels of a raster

[Rainer M Krug]

On Fri, Jul 1, 2011 at 2:06 PM, Luisa Peña <luisapena1979 at gmail.com> wrote:

> Hello Rainer
> I'm using reclass in order to have a raster with text lables (land use land
> cover class names). I thought that r.reclass would be the only way to have
> that.
> and My reclass file is something like this:
> 1 = 1 Urban
> 2 = 2 Agriculture
> 3 = 3 Irrigated Agriculture
> 4 = 4 Forests
> 5 = 5 Shrubland
> * = NULL
> Do you have any alternative suggestion to have labels in LULC?
>

It depends what you want to do with the raster.

For labelling, this is the right approach.

So when you use r.mapcalc "new_map=@existing_map"

this will assume that the labels of your input map are numeric. Are your
labels numeric or characters?

>From the help:

##########################
RASTER MAP LAYER VALUES FROM THE CATEGORY FILE

Sometimes it is desirable to use a value associated with a category's label
instead of the category value itself. If a raster map layer name is preceded
by the @ operator, then the labels in the category file for the raster map
layer are used in the expression instead of the category value.
For example, suppose that the raster map layer soil.ph (representing soil pH
values) has a category file with labels as follows:

cat label
------------------
0 no data
1 1.4
2 2.4
3 3.5
4 5.8
5 7.2
6 8.8
7 9.4
Then the expression:

result = @soils.ph
would produce a result with category values 0, 1.4, 2.4, 3.5, 5.8, 7.2, 8.8
and 9.4.

Note that this operator may only be applied to raster map layers and
produces a floating point value in the expression. Therefore, the category
label must start with a valid number. If the category label is integer, it
will be represented by a floating point number. I the category label does
not start with a number or is missing, it will be represented by NULL (no
data) in the resulting raster map.
##########################


Cheers,

Rainer


> THanks
> Luisa
>
> 2011/7/1 Rainer M Krug <r.m.krug at gmail.com>
>
>>
>>
>> On Fri, Jul 1, 2011 at 1:24 PM, Luisa Peña <luisapena1979 at gmail.com>wrote:
>>
>>> It didn't work. I get all full of NaNs map.
>>> I used this:
>>>     input="LUlabel at Study"
>>>     grass.run_command("g.region", rast = input)
>>>     grass.mapcalc("$output= @$labels", labels=input, output="Giovanni2")
>>>
>>> What am I doing wrong on this?
>>>
>>
>> NaN means Not a Number - were your labels non-numeric?
>> I *think* that raster can only have numeric cell values
>>
>> Rainer
>>
>>
>>
>>>  Luisa
>>>
>>> 2011/7/1 Giovanni Manghi <giovanni.manghi at gmail.com>
>>>
>>>> Hi,
>>>>
>>>>
>>>> >
>>>> > I have a raster map to wich I have applied r.reclass to add labels to
>>>> > raster classes.  When I try to export this raster with the classes I
>>>> > loose the lablels I only stick with the values.
>>>> > In a script how can edit this raster in order to be exported with the
>>>> > labels?Thanks
>>>>
>>>>
>>>> r.mapcalc "new_map=@existing_map"
>>>>
>>>> then export "new_map" to tiff as usual.
>>>>
>>>> Cheers
>>>>
>>>> -- Giovanni --
>>>>
>>>>
>>>>
>>>
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>>>
>>>
>>
>>
>> --
>> Rainer M. Krug, PhD (Conservation Ecology, SUN), MSc (Conservation
>> Biology, UCT), Dipl. Phys. (Germany)
>>
>> Centre of Excellence for Invasion Biology
>> Stellenbosch University
>> South Africa
>>
>> Tel :       +33 - (0)9 53 10 27 44
>> Cell:       +33 - (0)6 85 62 59 98
>> Fax (F):       +33 - (0)9 58 10 27 44
>>
>> Fax (D):    +49 - (0)3 21 21 25 22 44
>>
>> email:      Rainer at krugs.de
>>
>> Skype:      RMkrug
>>
>>
>


-- 
Rainer M. Krug, PhD (Conservation Ecology, SUN), MSc (Conservation Biology,
UCT), Dipl. Phys. (Germany)

Centre of Excellence for Invasion Biology
Stellenbosch University
South Africa

Tel :       +33 - (0)9 53 10 27 44
Cell:       +33 - (0)6 85 62 59 98
Fax (F):       +33 - (0)9 58 10 27 44

Fax (D):    +49 - (0)3 21 21 25 22 44

email:      Rainer at krugs.de

Skype:      RMkrug
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