[GRASS-user] v.kernel - Points weighted with attribute ?

Taïs tgrippa at ulb.ac.be
Tue Oct 22 04:33:34 PDT 2019

Hi Micha, thanks for your repply.

For my own need, I think your solution is enough and I would like to try 
if you agree to send the R script.

Le 22/10/19 à 12:53, Micha Silver a écrit :
> On 10/21/19 1:33 PM, Tais wrote:
>> Hi all,
>> I would like to compute a raster density map ("heat map") from vector 
>> points using v.kernel. The points represent house addresses. However, 
>> I would need to weight the points with a value stored in the 
>> attribute table (number of inhabitants). I saw on the module manual 
>> page that this functionality is a "known issue".
>> I imagined a solution to by-passe the limitation: duplicate each 
>> point as many time as needed (according to the value stored in the 
>> attribute table) and use this new layer directly in v.kernel. 
>> However, I think it will definitely not be the most efficient way to 
>> do the trick. Do you have an alternative in mind ?
>> Of course the best solution would be that someone in the development 
>> community would have the time and the kindness to implement this 
>> function directly in the module (I'm not skilled in C and thus cannot 
>> try myself).
> Maybe not the answer you are looking for, but you can create a 
> weighted kernel density in R. I can send an R script that is intended 
> to be run from within a GRASS session. It accepts a point vector and 
> attrib column, and creates a kernel density raster, weighted by the 
> attribute values (using the R defaults for bandwidth and Gaussian kernel)
> Requires, of course, that R is installed, with the packages: spatstat, 
> raster, rgrass7.
>> NB: Sorry if I should have posted this on the developer mailing list. 
>> I hesitated but decided to post here finally.
>> Best,
> -- 
> Micha Silver
> Ben Gurion Univ.
> Sde Boker, Remote Sensing Lab
> cell: +972-523-665918
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