[GRASS-user] Probabilistic neighborhood analysis

[Veronica Andreo]

Hi Bernardo,

Yes, feel free to open a feature request issue. You can assign it to
yourself if you think you may tackle it afterwards.

Cheers,
Vero

El lun, 16 ene 2023 a las 19:20, Bernardo Santos via grass-user (<
grass-user at lists.osgeo.org>) escribió:

> Hi Makus,
>
> Nice suggestion, I did not know about this function within r.mapcalc (it
> is quite hidden!)
> I still do not know how to operationalize it, though.
> For now, the solution with R worked, but it could be useful to have
> something like that in GRASS in the future.
> Should I open an issue with a suggestion?
> (I do not have time to do it right now)
>
> Best
> Bernardo
> Em quarta-feira, 11 de janeiro de 2023 09:39:17 GMT+1, Markus Neteler <
> neteler at osgeo.org> escreveu:
>
>
> Hi Bernardo,
>
> Not sure if this helps but there is also this function in r.mapcalc:
>
> https://grass.osgeo.org/grass78/manuals/r.mapcalc.html
>
> graph(x,x1,y1[x2,y2..])        convert the x to a y based on points
> in a graph F
> graph2(x,x1[,x2,..],y1[,y2..]) alternative form of graph()
>
> The graph() function allows users to specify a x-y conversion using
> pairs of x,y coordinates. In some situations a transformation from one
> value to another is not easily established mathematically, but can be
> represented by a 2-D graph and then linearly interpolated. The graph()
> function provides the opportunity to accomplish this. An x-axis value
> is provided to the graph function along with the associated graph
> represented by a series of x,y pairs. The x values must be
> monotonically increasing (each larger than or equal to the previous).
> The graph function linearly interpolates between pairs. Any x value
> lower the lowest x value (i.e. first) will have the associated y value
> returned. Any x value higher than the last will similarly have the
> associated y value returned.
> [...]
>
> Perhaps a dynamic (set of) graphs could be constructed?
>
> Best,
> Markus
>
> On Wed, Dec 14, 2022 at 2:37 PM Bernardo Santos via grass-user
> <grass-user at lists.osgeo.org> wrote:
> >
> > Hi,
> >
> > I am trying to produce scenarios of past land cover, before hydropower
> reservoirs were built. To do so, I need to fill empty pixels from a raster
> in the locations where the reservoirs are currently present, using as input
> the actual land cover map. I tried doing that with r.neighbors (taking
> method=mode) with neighborhoods of increasing size, to replace null pixels
> with the most common land cover class in the neighborhood. I also tried
> that with r.fill.stats which is basically the same thing.
> > However, the results gets very homogeneous, since the interpolated null
> cells always get the value of the most common land cover class.
> >
> > Do anyway know of a method in GRASS to perform a "probabilistic"
> neirighborhood analysis, where cells in a neighborhood are given weights
> (possibly related to the distance to the central cell and to their
> frequency) and these weights are used to stocastically sample a value to
> fill the central cell?
> > If not in GRASS, does anyway know of such a method in a different
> platform, i.e. R?
> >
> > Thanks!
> > Best
> > Bernardo
> > _______________________________________________
> > grass-user mailing list
> > grass-user at lists.osgeo.org
> > https://lists.osgeo.org/mailman/listinfo/grass-user
>
>
>
> --
> Markus Neteler, PhD
> https://www.mundialis.de - free data with free software
> https://grass.osgeo.org
> https://courses.neteler.org/blog
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>
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