[R-sig-Geo] R-sig-Geo Digest, Vol 138, Issue 4

[Karloz]

r-sig-geo-request at r-project.org wrote:

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>Today's Topics:
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>   1. Re: grid in adehabitatHR (chirleu)
>
>
>----------------------------------------------------------------------
>
>Message: 1
>Date: Tue, 3 Feb 2015 07:37:27 -0700 (MST)
>From: chirleu <chirleu at gmail.com>
>To: r-sig-geo at r-project.org
>Subject: Re: [R-sig-Geo] grid in adehabitatHR
>Message-ID:
>	<CALC46t_qMTRveZJvRCFxFb+FeU1hVrK21Cyphgm_2hXTYMkmFQ at mail.gmail.com>
>Content-Type: text/plain; charset=us-ascii
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>Hi Jed,
>It worked! So thank you. I was close. I think I was passing a complet grid
>(not only 4 points):
>loc4=raster(loc,nrows=1000,ncols=1000)
>but for some reason did not work. It seems the key is the expand.grid
>function.
>
>Cheers,
>
>David
>
>2015-02-03 10:52 GMT+01:00 JLong [via R-sig-geo] <
>ml-node+s2731867n7587727h27 at n2.nabble.com>:
>
>> Hi David,
>>
>> The kernelUD 'grid' parameter expects a SpatialPixels object that
>> represents the raster upon which you wish to estimate the animal UD. You
>> are passing in only a raster with 4 pixels, which I think represent the
>> outer corners of the raster upon which you wish to estimate the UD.
>> Alternatively, the grid parameter can accept a number that represents the
>> pixel size, and it will automatically build the raster for you.
>>
>> The problem lies in your buildup definition of the SpatialPixelsDataFrame
>> object. When you define a 'grid' you need to identify the locations of each
>> pixel in the grid and save those as columns x  and y  in the data frame.
>> See the 'expand.grid' function and the meuse.grid example in the function
>> 'coordinates'.
>>
>> As a test just try:
>> kud=kernelUD(detections[,1],h=h, grid=40, kern=c("bivnorm"))
>>
>>
>> Then, the process if you wish to define your own grid would then be:
>> x <- seq(xmin,xmax,by=resolution)  # where resolution is the pixel size
>> you desire
>> y <- seq(ymin,ymax,by=resolution)
>> xy <- expand.grid(x=x,y=y)
>> coordinates(xy) <- ~x+y
>> gridded(xy) <- TRUE
>> class(xy)
>>
>> kud=kernelUD(detections[,1],h=h, grid=xy, kern=c("bivnorm"))
>>
>> Cheers,
>> Jed
>>  Jed Long
>> Lecturer in GeoInformatics
>> Department of Geography & Sustainable Development
>> University of St Andrews, UK
>>
>>
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>End of R-sig-Geo Digest, Vol 138, Issue 4
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