[R-sig-Geo] gIntersection for several polygons

[Bernd Vogelgesang]

Hi Rebecka,

I can't help you with your homerange problem right now, but maybe give you  
a hint about the intersection.
I also unsuccesfully tried to use gIntersection until I was told that the  
raster (!) package has a function "intersection" which worked perfectly  
for me.

My last R-project was also on wind farms, where I had to calculate  
presence values for different species and two buffers for each single  
turbine. Maybe sth of this is useful for you (though horribly coded I  
fear). In case ... drop me a line.

Cheers
Bernd


Am 11.11.2014, 10:09 Uhr, schrieb Rebecka <rehe0001 at stud.slu.se>:

> Hi!
>
> I´m a beginner with R and I´m trying to calculate area of polygons
> (homerange areas of 31 individuals) intersecting with bufferzones around
> 4348 number of windfarms. I have read this webpage as a help:
> http://rstudio-pubs-static.s3.amazonaws.com/7993_6b081819ba184047802a508a7f3187cb.html
>
> I´ve succeeded to create bufferzones with gBuffer. Now I would like to do
> gIntersection for every individuals homerange overlap with bufferzones.  
> I´ve
> tried to create homeranges as a first step using gConvexHull but I don´t
> understand how to this by each id for every individual. I have a
> spatialpointsdataframe with one column called "Object_ID" and also  
> columns
> "x" and "y" for coordinates and every row corresponds to one position.  
> Every
> individual have a lot of coordinates (all individuals have over 94000
> positions together).
>
> Is it possible to create one homerange for every individual using
> gConvexHull? byid=TRUE just do it for every row when I tried.
>
> I also tried to go around the problem creating mcp (packageadehabitatHR)  
> for
> every individual.
> mcpAll<-mcp(animalSpdf[,2]) *gives Spatialpolygons*
>
> Then I tried to use that in gIntersection
> inter1<-gIntersection(mcpAll,Prop1,byid=TRUE) *Prop1 is my windfarms with
> bufferzones*
> but it only gave a NULL result for inter1. CRS are same for both and I  
> know
> that they should overlap.
>
> Any ideas how to solve this?
>
> Thanks!!
>
> Rebecka Hedfors
>
>
>
>
> --
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>
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-- 
Bernd Vogelgesang
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