[GRASS-user] GRASS64 - r.mapcalc - replacement of specifics value by a mean of nearest neigbour
Paulo van Breugel
p.vanbreugel at gmail.com
Sat May 4 11:45:01 PDT 2013
One way to do this would be to replace all values between 4 and 7 by
NULL (e.g., r.null map=yourRaster setnull=4-7). Then use r.neighbors to
calculate the mean of the nearest neighbors (e.g., r.neighbors
input=yourRaster output=intermediateResult size=3. Have a look at the
help file of r.neighbors and the part about the size of the neighborhood
and option to use a circular neighborhood). Last step, patch the two
layers together (e.g, r.patch input=yourRaster,intermediateResult
output=yourOutput).
As for your second question, r.stats is indeed what you are looking for
I think, it calculates the surface for each categories of the input
raster layer.
Rgds
Paulo
On 05/04/2013 08:17 PM, BLANDENIER Lucien wrote:
> Dear Grass users,
>
> I'm working with rasters maps of large area and I want to calculate surface related to specific colours. Before this, I have to replace the surfaces of the rivers by the surrounding value (or the mean of the surrounding value).
>
> I looked at the manual of r.mapcalc but I didn't found how to do this...
>
> For instance, I want to replace all value between 4 and 7 by the mean of the value of the 4 nearest pixels.
>
> Is there any way of doing this?
>
> Which command shall I use then for calculating the surface for each color? r.stats? or is there a command that directly computes the surface?
>
>
> Best regards
>
>
> Lucien
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