Hi Micha El jue., 31 oct. 2019 a las 22:36, Micha Silver (<[email protected]>) escribió:
> > On 31/10/2019 22:20, Markus Metz wrote: > > > > On Tue, Oct 29, 2019 at 7:40 PM Veronica Andreo <[email protected]> > wrote: > > > > Hi Daniel, > > > > I agree that if there's a NULL in the column, there should be NULL in > the resulting raster. I suggest to open a ticket here: > https://trac.osgeo.org/grass/ > > easy solution: v.to.rast where="<attribute_column> is not null" > > or the new PR #173 > https://github.com/OSGeo/grass/pull/173 > if an attribute value is null, the corresponding vector features will not > be rasterized > > Markus M > > I'm not sure I agree with the approach that a polygon with missing > attribute should become NULL. In my view, NULL should be used only for > pixels not covered at all by any polygon. > but in the resulting raster (in rasters in general), there's no difference, it's rather NULL or it has a value... it does not matter if the null comes from areas originally covered by a polygon or not... A different story might be if we go from raster to polygon... > Perhaps an additional input parameter "missing_attribute" so the user can > choose a value to enter into the raster if the attribute is missing. If no > parameter is supplied, and the chosen attribute column has missing values, > I'd prefer that the script exit gracefully, with a message that a > "missing_attribute" value is required. > yes, this could be a solution to keep track of where you had polygons, but then you would need to use r.null anyway, no? I try to think of use cases in which one uses a vector attribute to convert to raster, but then still needs to know where the polygons were... because, for example, to query a raster map with another raster map representing zones one would convert the vector of polygons using cat and not an attribute, no? cheers, Vero > > > El jue., 24 oct. 2019 a las 14:40, Daniel Victoria (< > [email protected]>) escribió: > >> > >> Hi list, > >> > >> I have a vector polygon map that I'm converting to raster. The > attribute column that I process has some empty rows (no data / null). When > I run v.to.rast, these empty rows become 0 (zero) on my resulting raster > map. > >> > >> Shouldn't v.to.rast respect the empty attribute table and create null > values for those polygons? > >> > >> For now I'll use r.null to fix this problem. But what if 0 is a valid > value? > >> > >> Cheers > >> Daniel > >> > >> PS - Running Grass 7.6.1 on Ubuntu > >> _______________________________________________ > >> grass-user mailing list > >> [email protected] > >> https://lists.osgeo.org/mailman/listinfo/grass-user > > > > _______________________________________________ > > grass-user mailing list > > [email protected] > > https://lists.osgeo.org/mailman/listinfo/grass-user > > _______________________________________________ > grass-user mailing > [email protected]https://lists.osgeo.org/mailman/listinfo/grass-user > > -- > Micha Silver > Ben Gurion Univ. > Sde Boker, Remote Sensing Lab > cell: +972-523-665918 > >
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