[GRASS-dev] Random selection of a given number of points/pixels per class

Dear devs,

Recently, I was trying to generate a fixed number of random points per class in a vector or raster map.

So I looked at both v.random and r.random. However, neither seemed to give me the desired result:

v.random with restrict option seems to generate points per area even if areas belong to the same class and share the same cat value.

r.random does not have a restrict option.

So I ended up writing a small script that basically loops over the classes and extracts n points/pixels per class from a input raster map. My question now is did I overlook some less obvious feature of v.random or r.random?

If not I might create a small wrapper addon…

Cheers

Stefan

r.sample.category in addons seems like what you want?

On Fri, Aug 30, 2019 at 3:59 AM Stefan Blumentrath <Stefan.Blumentrath@nina.no> wrote:

Dear devs,

Recently, I was trying to generate a fixed number of random points per class in a vector or raster map.

So I looked at both v.random and r.random. However, neither seemed to give me the desired result:

v.random with restrict option seems to generate points per area even if areas belong to the same class and share the same cat value.

r.random does not have a restrict option.

So I ended up writing a small script that basically loops over the classes and extracts n points/pixels per class from a input raster map. My question now is did I overlook some less obvious feature of v.random or r.random?

If not I might create a small wrapper addon…

Cheers

Stefan


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https://lists.osgeo.org/mailman/listinfo/grass-dev

Yes, thanks! Thats it. Thanks also for reviewing the PR so quickly!

Cheers

Stefan

···

r.sample.category in addons seems like what you want?

On Fri, Aug 30, 2019 at 3:59 AM Stefan Blumentrath <Stefan.Blumentrath@nina.no> wrote:

Dear devs,

Recently, I was trying to generate a fixed number of random points per class in a vector or raster map.

So I looked at both v.random and r.random. However, neither seemed to give me the desired result:

v.random with restrict option seems to generate points per area even if areas belong to the same class and share the same cat value.

r.random does not have a restrict option.

So I ended up writing a small script that basically loops over the classes and extracts n points/pixels per class from a input raster map. My question now is did I overlook some less obvious feature of v.random or r.random?

If not I might create a small wrapper addon…

Cheers

Stefan


grass-dev mailing list
grass-dev@lists.osgeo.org
https://lists.osgeo.org/mailman/listinfo/grass-dev