Hi Nils-
I wrote an R function for something like this a while back.  It is designed
to sample time-series grids (.asc grid format) associated with fish
telemetry data. If you have high quality telemetry data (ie. GPS) it will
sample just the pixel 'underneath' locations, but if your telemetry data
have quite a bit of uncertainty (as my fish data do), it will sample a user
defined probability cloud around each observation, and compute the weighted
mean of pixels contained within the cloud. Although I have sampled some
pretty large time-series datasets with it, it probably isn't as efficient as
it could be. I suspect some improvements could be made to get it working
more efficiently, but if you are willing to let it run for a while, and can
convert your data to the correct format, it might help.

Drop me a note if you are interested.

Tim Sippel - Post-doctoral Researcher
University of Hawaii


> Message: 16
> Date: Fri, 7 Jan 2011 10:37:32 +0000
> From: "Breitbach, Nils" <breitbach@uni-mainz.de>
> To: r-sig-geo <r-sig-geo@stat.math.ethz.ch>
> Subject: [R-sig-Geo] Habitat on a given location (spatial join with R)
> Message-ID:
>        <
> E7F1EF063B11DA4DAD16374549B879E82AE5C4B5@e14mdb-02.zdv.Uni-Mainz.DE>
> Content-Type: text/plain; charset="us-ascii"
>
> Derar community,
>
> this time I need to find habitat type on given location for a huge number
> of points. I have two layers: the first (upper) one is a point shape with
> approx. 100,000 point locations; the second one is a polygon shape with many
> features containing habitat types (on a very fine scale). Now, I need the
> habitat type "under" every point or better said for every point location.
>
> The "Spatial Join" Tool in ESRI's ArcGIS  would do exactly what I need but
> since I did all my analyses with R so far I really would like to avoid the
> permanent jumping between R and ArcGIS. Is there a function in R that solves
> my problem?
>
> Cheers,
>
> Nils
>
>
>
>

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