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

[chris english]

Mel,

Sorry, your pseudo-code:

raster::extract(udel, admin, fun=mean, na.rm=T, small=T, weights = TRUE)

Chris

On Tue, Oct 18, 2016 at 6:10 PM, chris english <
englishchristophera at gmail.com> wrote:

> 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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>

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