[GRASS-user] Creating spatially clumped random cells

[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
>
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