[GRASS-user] r.clump with diagonal cells

[Johannes Radinger]

Thanks for the hint about r.clump2.

I just tried to apply it to my data. While this tool works with diagonally
connected cells (in contrast to r.clump) it does not preserve the distinct
category values of adjacent cells. Furthermore, as also mentioned in the
manual: Linear elements are always clumped together, unless the e-flag is
set (which basically ignores diagonally connected cells and thus is
comparable to r.clump result). So as I'd like to have unique category
values for the single (adjacent) patches this tool does not necessarily
help me. However, good to know that there is such a tool available. For the
moment, I'll try an approach to buffer (r.grow) my raster lines before
applying r.clump which could work.

best,
Johannes


On Mon, Jan 13, 2014 at 3:30 PM, Markus Neteler <neteler at osgeo.org> wrote:

> On Mon, Jan 13, 2014 at 12:39 PM, Johannes Radinger
> <johannesradinger at gmail.com> wrote:
> > Dear all,
> >
> > I just tried r.clump on a rastarized river with alternating patches of
> good
> > and bad habitat (values 1 and 2). However, due to its linear structure,
> many
> > cells of the same habitat patch are often only diagonally connected. So
> this
> > is a case where r.clump does not work (as stated in its manual).
> >
> > So, as a suggestion, it'd be nice if also diagonal cells could be
> considered
> > by r.clump (e.g. by setting a flag).
>
> Note that there is a more modern version here:
>
> http://grasswiki.osgeo.org/wiki/AddOns/GRASS_6#r.clump2
>
> http://grasswiki.osgeo.org/wiki/AddOns/GRASS7/raster#r.clump2
>
> Markus
>
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