[R-sig-eco] problem with kernel UD estimation using adehabitatHR

[lnmessinger]

I have data containing locations of 100+ pheasants during 3 seasons. I am
looking to estimate kernel home ranges for each of the seasons for each
individual. I run the kernelUD() function with no errors or warnings, but am
receiving an error message when I attempt to use the getverticeshr() and
kernel.area() functions to extract 95% polygons and area estimates from the
kernel UD's.

Here is the structure of the input data set:

Formal class 'SpatialPointsDataFrame' [package "sp"] with 5 slots
  ..@ data       :'data.frame':	2376 obs. of  1 variable:
  .. ..$ ID: Factor w/ 122 levels "150.002_2013_KOR",..: 1 1 1 1 1 1 2 2 2 2
...
  ..@ coords.nrs : num(0) 
  ..@ coords     : num [1:2376, 1:2] 347887 347862 347948 347964 348200 ...
  .. ..- attr(*, "dimnames")=List of 2
  .. .. ..$ : NULL
  .. .. ..$ : chr [1:2] "X_Estimate" "Y_Estimate"
  ..@ bbox       : num [1:2, 1:2] 315869 4442294 349590 4472129
  .. ..- attr(*, "dimnames")=List of 2
  .. .. ..$ : chr [1:2] "X_Estimate" "Y_Estimate"
  .. .. ..$ : chr [1:2] "min" "max"
  ..@ proj4string:Formal class 'CRS' [package "sp"] with 1 slots
  .. .. ..@ projargs: chr NA

The following code works without errors or warnings for my "pre" season
data:

kud.pre<-kernelUD(pre.hr.id[,1],h="href",extent=1)
pre.hr.poly<-getverticeshr(kud.pre, percent=95)
pre.kud.area<-kernel.area(kud.pre,percent=95)

However, when I repeat my other 2 seasons, kernelUD() runs with no errors or
warnings:

kud.early<-kernelUD(early.hr.id[,1],h="href",extent=1)

but I get the following error when running the getverticeshr() function:

early.hr.poly<-getverticeshr(kud.early, percent=95)

Error in getverticeshr.estUD(x[[i]], percent, ida = names(x)[i], unin,  : 
  The grid is too small to allow the estimation of home-range.
You should rerun kernelUD with a larger extent parameter

I have adjusted the extent parameter as requested, using values of
0.5,1,5,10,25,100 and all produce the same error. I am able to generate
mcp's using the same data without a problem and like I said, kernelUD()
works with no errors or warnings for all 3 seasons and I am able to see each
UD when I look at the image.

What I find particularly strange is that I am able to run kernel.area() and
even with warnings that say:

1: In kernel.area(j, percent, unin, unout) :
  The grid is too small to allow the estimation of home-range
for the following value of percent: 95. You should rerun kernelUD with a
larger extent parameter

I still get a data frame with area values for each individual. It seems as
if an area is estimated regardless of the error warning of small extent
size.

Has anyone experienced a similar issue or have a suggestion as to how I
should proceed?

Thanks,
Lindsey






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