[GRASS-user] Get sums of raster values based on the categories of an overlay raster

GRASS GRASS user
1

Hi,

I’d like to calculate the sum of all raster values that belong to a certain group. This spatially organized group is also indicated by an overlay raster (same resolution). Finally I want to assign these sums to a new raster. That might sound slightly complicated but here an example:

Asume following initial raster map A with random values like:

1-2-1-1-3-4-3-4-2-5-2-3

and an overlay raster indicating 3 groups:

1-1-1-1-2-2-2-2-3-3-3-3

the sums for the groups are:
group 1 = 5
group 2 = 14
group 3= 12

so the final raster would be:

5-5-5-5-14-14-14-14-12-12-12-12

How can such a task be achieved in GRASS (7)?
Any ideas?

/Johannes

2

On 26/11/13 16:28, Johannes Radinger wrote:

Hi,

I'd like to calculate the sum of all raster values that belong to a
certain group. This spatially organized group is also indicated by an
overlay raster (same resolution). Finally I want to assign these sums to
a new raster. That might sound slightly complicated but here an example:

Asume following initial raster map A with random values like:

1-2-1-1-3-4-3-4-2-5-2-3

and an overlay raster indicating 3 groups:

1-1-1-1-2-2-2-2-3-3-3-3

the sums for the groups are:
group 1 = 5
group 2 = 14
group 3= 12

so the final raster would be:

5-5-5-5-14-14-14-14-12-12-12-12

How can such a task be achieved in GRASS (7)?
Any ideas?

r.statistics ?

Moritz

3

Yes of course, r.statistics resp. r.statistics2 is doing the job. I just mixed up the the maps when I tried it the first time.
Thanks Markus and Moritz!

···

On Thu, Nov 28, 2013 at 9:22 AM, Moritz Lennert <mlennert@club.worldonline.be> wrote:

On 26/11/13 16:28, Johannes Radinger wrote:

Hi,

I’d like to calculate the sum of all raster values that belong to a
certain group. This spatially organized group is also indicated by an
overlay raster (same resolution). Finally I want to assign these sums to
a new raster. That might sound slightly complicated but here an example:

Asume following initial raster map A with random values like:

1-2-1-1-3-4-3-4-2-5-2-3

and an overlay raster indicating 3 groups:

1-1-1-1-2-2-2-2-3-3-3-3

the sums for the groups are:
group 1 = 5
group 2 = 14
group 3= 12

so the final raster would be:

5-5-5-5-14-14-14-14-12-12-12-12

How can such a task be achieved in GRASS (7)?
Any ideas?

r.statistics ?

Moritz