[R-sig-Geo] problem with rasterToPolygons x worldclim

[Karla Shikev]

Hi Michael,

Thanks for the tips. I tried the help for rasterToPolygons, but none of the
options (e.g. dissolve=TRUE) made any difference. I tried gPolygonize and
it worked, except for (as you predicted), if the edges meet the raster
extents - but that definitely was an advance!

I really appreciate your help and if you just point the way I can try to go
after what needs to be done, but right now I´m stumped.

best, Karla.

On Mon, Apr 4, 2016 at 5:38 PM, Michael Sumner <mdsumner at gmail.com> wrote:

> Read the help for rasterToPolygons, alternatively try chaining
> rasterToContour and rgeos::gPolygonize.
>
> The latter may need coaxing if your edges meet the raster extents.
>
> Cheers, Mike
>
> On Tue, 5 Apr 2016, 05:32 Karla Shikev <karlashikev at gmail.com> wrote:
>
>> Dear all,
>>
>> Here's an issue that is related to the previous one. In the commands below
>> I'm trying to make a polygon for all the regions within a range of mean
>> annual temps. However, rasterToPolygons will draw a square around each
>> value in the original raster, rather than providing me the actual polygon,
>> given that resolution. Any hints? Again, any help will be greatly
>> appreciated.
>>
>> Karla
>>
>> _____
>>
>> library(raster)
>>
>> r<-getData('worldclim', var='bio', res=10)$bio1
>>
>> e <- extent(-140,-100, 50, 60)
>>
>> xx<-crop(r,e)
>>
>> slice1<-rasterToPolygons(xx, fun = function(x) {x > 40 & x < 60})
>>
>> plot(slice1)
>>
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>>
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> --
> Dr. Michael Sumner
> Software and Database Engineer
> Australian Antarctic Division
> 203 Channel Highway
> Kingston Tasmania 7050 Australia
>
>

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