[R-sig-Geo] Extract() fails to return data for boundary admin units

[chris english]

Mel,

Looking at detail in cjg.png the northmost missing data island shows approx
20-25 in Southern three quarters and 0-5 the small North at tip of island.
Directly above this 0-5 another coastal 0-5.
If a substantial east-west scarp bisected the island it might explain. I
would otherwise expect a very slight mismatch in projection, a thing I
often have problems with.

Though reading raster::extract it looks like you want to employ the weights
are if your polys are relatively smaller than your cells.

HTH
Chris

On Oct 18, 2016 4:35 PM, "Bacou, Melanie" <mel at mbacou.com> wrote:

> Hi,
> I'm summarizing biophysical rasters (UDEL precipitation and temperature)
> across administrative units for countries in Africa using (pseudo code):
>
> raster::extract(udel, admin, fun=mean, na.rm=T, small=T)
>
> Out of the 756 units I need data for, extract() fails to return means for
> a few coastal units (in red on the maps below) even though the rasters show
> data at these locations.
>
> Is there a particular reason why this might happen? Shall I look for
> possible geometry errors in my source shapefiles, or could there be another
> reason?
>
> Maps here:
> https://dl.dropboxusercontent.com/u/30925475/eclgcdmhapfplaml.png
> https://dl.dropboxusercontent.com/u/30925475/lmkgmdoohpmhdcjg.png
>
> Thanks for any tip. --Mel.
>
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