[R-sig-Geo] Warning in st_intersection

[Sergio Ibarra]

So, I need to know the attribute geometry relationship (agr) (constant,
aggregate or identity)  of each variable of mine data set

Thank you Edzer


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*Sergio Ibarra Espinosa*
MSc Environment, PhD Meteorology, Departamento de Ciências Atmosféricas,
Universidade de São Paulo
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Em qui, 6 de jul de 2017 às 12:37, Edzer Pebesma <
edzer.pebesma at uni-muenster.de> escreveu:

>
>
> On 06/07/17 16:16, Sergio Ibarra wrote:
> > Hello everyone
> >
> > In my work, I use to intersect polygon grids with lines or points. I use
> > the package "sf" with the function 'st_intersection". However, every
> time I
> > run st_intersection I got the following Warning Message:
> >
> > Warning message:attribute variables are assumed to be spatially
> > constant throughout all geometries
> >
> >
> > What does this warning mean?
>
> Attribute values are assigned to sub-geometries; if these are spatially
> constant, as for instance for land use, then this is fine. If they are
> aggregates, such as population count, then this is not fine, wrong even.
> By default, they are set to NA.
>
> e.g.
>
> demo(nc)
> st_agr(nc) = "constant"
>
> takes away the warning, as it sets all attribute values (in this case
> wrongly) to "constant", as of their agr value (agr standing for
> "attribute geometry relationship").
>
> More here:
>
> https://cran.r-project.org/web/packages/sf/vignettes/sf1.html#how-attributes-relate-to-geometries
>
> >
> > Thanks
> >
>
> --
> Edzer Pebesma
> Institute for Geoinformatics  (ifgi),  University of Münster
> Heisenbergstraße 2, 48149 Münster, Germany; +49 251 83 33081
> <+49%20251%208333081>
> Journal of Statistical Software:   http://www.jstatsoft.org/
> Computers & Geosciences:   http://elsevier.com/locate/cageo/
>
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-- 
​Sergio Ibarra Espinosa
Doutorando em Meteorologia
Instituto de Astronomia, Geofísica e Ciências Atmosféricas
Universidade de São Paulo
Rua do Matão, 1226
Cidade Universitária
São Paulo-SP - Brasil -
05508-090
+55-11-3091-2833
+55-11-97425-3791
Skype: sergio_ibarra1
Blog: www.sergioibarra.blogspot.com


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*Sergio Ibarra Espinosa*
MSc, Departamento de Ciências Atmosféricas, Universidade de São Paulo
+ 55 11 3091-4731 <+%2055%2011%203091-4731> | +55 11 974 253 791
<+55%2011%20974%20253%20791> | sergio.ibarra at iag.usp.br |
www.sergioibarra.blogspot.com | Skype: sergio_ibarra1 <#> | Rua do Matão,
1226 - Cidade Universitária São Paulo-SP - Brasil - 05508-090
<http://us.linkedin.com/in/sibarra>  <http://twitter.com/sergio_ibarra>
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