<div dir="ltr"><div dir="ltr">Hi Micha<br></div><br><div class="gmail_quote"><div dir="ltr" class="gmail_attr">El jue., 31 oct. 2019 a las 22:36, Micha Silver (<<a href="mailto:tsvibar@gmail.com" target="_blank">tsvibar@gmail.com</a>>) escribió:<br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">
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<div>On 31/10/2019 22:20, Markus Metz wrote:<br>
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On Tue, Oct 29, 2019 at 7:40 PM Veronica Andreo <<a href="mailto:veroandreo@gmail.com" target="_blank">veroandreo@gmail.com</a>>
wrote:<br>
><br>
> Hi Daniel,<br>
><br>
> 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: <a href="https://trac.osgeo.org/grass/" target="_blank">https://trac.osgeo.org/grass/</a><br>
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</div>
<div>easy solution: v.to.rast where="<attribute_column> is
not null"</div>
<div><br>
</div>
<div>or the new PR #173</div>
<div><a href="https://github.com/OSGeo/grass/pull/173" target="_blank">https://github.com/OSGeo/grass/pull/173</a></div>
<div>if an attribute value is null, the corresponding vector
features will not be rasterized</div>
<div><br>
</div>
<div>Markus M</div>
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<p>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. </p></div></blockquote><div>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... <br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><div bgcolor="#FFFFFF">
<p>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.</p></div></blockquote><div>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?<br></div><div><br></div><div>cheers, <br></div><div>Vero<br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><div bgcolor="#FFFFFF">
<blockquote type="cite"><br><div dir="ltr">
> El jue., 24 oct. 2019 a las 14:40, Daniel Victoria (<<a href="mailto:daniel.victoria@gmail.com" target="_blank">daniel.victoria@gmail.com</a>>)
escribió:<br>
>><br>
>> Hi list,<br>
>><br>
>> 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.<br>
>><br>
>> Shouldn't v.to.rast respect the empty attribute table
and create null values for those polygons?<br>
>><br>
>> For now I'll use r.null to fix this problem. But what
if 0 is a valid value?<br>
>><br>
>> Cheers<br>
>> Daniel<br>
>><br>
>> PS - Running Grass 7.6.1 on Ubuntu<br>
>> _______________________________________________<br>
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>> <a href="https://lists.osgeo.org/mailman/listinfo/grass-user" target="_blank">https://lists.osgeo.org/mailman/listinfo/grass-user</a><br>
><br>
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</blockquote>
<pre cols="72">--
Micha Silver
Ben Gurion Univ.
Sde Boker, Remote Sensing Lab
cell: +972-523-665918</pre>
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