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 <[email protected]> wrote: > On Thu, Jan 9, 2014 at 4:09 PM, Johannes Radinger > <[email protected]> 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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