[GRASS-user] Creating spatially clumped random cells

[Johannes Radinger]

Hi Martin,

r.pi.nlm sounds really suitable for such tasks, I should really have a look
into it. As I recognized you as one of the maintainers, do you think it'll
be available also as an add-on for GRASS7?

cheers,
Johannes


On Fri, Jan 10, 2014 at 11:59 AM, M Wegmann <wegmann2011 at gmail.com> wrote:

> Hi Johannes,
>
> you might want to look into the r.pi. suit[1]. You will find a command
> called
> r.pi.nlm which generates random landscapes based on some settings (e.g. %
> coverage).
>
> cheers, Martin
>
>
> http://svn.osgeo.org/grass/grass-addons/grass6/raster/r.pi/
>
>
> On Friday, January 10, 2014 09:57:12 AM Robert Nuske wrote:
> > Hi Johannes
> >
> > another path might be to use the excellent tools of the R package
> spatstat
> > to simulate various cluster processes. Those generated point patterns
> could
> > then be translated to rasters.
> >
> > Functions for random point processes exhibiting clustering in spatstat
> are
> > e.g. rThomas, rGaussPoisson, rMatClust, rcell  (retrieved from the help
> page
> > of rpoispp).
> >
> > The simulated point density will of course not always have exactly the
> > requested density.
> >
> >
> > cheers
> >   robert
> >
> > Am Freitag, 10. Januar 2014, 08:17:50 schrieb Johannes Radinger:
> > > Hi Markus,
> > >
> > > so far as I understood r.random.cell creates spatially most
> disaggregated
> > > cells (based on the distance parameter). So instead of clumping them
> this
> > > module does the opposite.
> > >
> > > However, I am just trying another solution which might be promising:
> With
> > > r.random.surface
> > > it is possible to generate a spatially dependent surface (like a
> landscape
> > > with mountains and valleys). Then I can use r.quantile to get the
> > > lowest/highest e.g 20% of all values and consequently I can use
> r.mapcalc
> > > to reclassify all values smaller than the threshold value I yielded
> from
> > > r.quantile. First trials yielded good results although the 20%
> threshold
> > > did not exactly translate into 20% of all cells. I've to investigate a
> > > little bit more into that. Any other suggestions?
> > >
> > > Best regards,
> > > Johannes
> > >
> > > On Fri, Jan 10, 2014 at 12:43 AM, Markus Neteler <neteler at osgeo.org>
> wrote:
> > > > On Thu, Jan 9, 2014 at 4:09 PM, Johannes Radinger
> > > >
> > > > <johannesradinger at gmail.com> wrote:
> > > > > Hi,
> > > > >
> > > > > just two short question concerning the creation of random cells.
> > > > > So far I used r.random to create e.g. a map with 20% cells (of my
> > > > > input
> > > > > raster).
> > > > > I'd like to know:
> > > > > 1) Is there a way to create randomly spatially clumped rasters
> cells
> > > > > so
> > > >
> > > > that
> > > >
> > > > > the cells
> > > > > look aggregated like patches, while still setting the e.g. 20%
> limit?
> > > >
> > > > Maybe
> > > >
> > > > > with a factor of spatial autocorrelation!? Maybe somebody has an
> > > > > example
> > > > > 2) Is there a way to set a fixed seed to make reproducible results
> > > > > with
> > > > > r.random and similar modules?
> > > >
> > > > While likely not a solution for you but take a look at
> > > > http://grass.osgeo.org/grass70/manuals/r.random.cells.html
> > > >
> > > > Markus
> >
> > _______________________________________________
> > grass-user mailing list
> > grass-user at lists.osgeo.org
> > http://lists.osgeo.org/mailman/listinfo/grass-user
>
>
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