[GRASS-user] r.clump with diagonal cells

[Markus Metz]

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

I would recommend r.clump4p over r.clump2. r.clump4p is the fastest of
the three, even without parallelisation. Note that r.clump4p, like
r.clump, also clumps NULL cells, whereas only r.clump2 ignores NULL
cells.

>
> Markus
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