[AniMov] Problem with kerneloverlap output when method=HR

Elodie Camprasse elodie.camprasse at gmail.com
Mon Aug 11 08:40:15 CEST 2014


G'day folks, 

I am encountering a problem when working with the function kerneloverlap in
the package adehabitatHR. I am trying to calculate the overlap in home
ranges within consecutive trips of the same animal. In order to use the
function, I first created the spatialPointsDataFrame object called example
from a dataframe that has in order, a column with the ID (trip number), one
column with Longitude, one column with Latitude and a column with a
timestamp (see attached csv) like this:

example_df<-SpatialPointsDataFrame(coords=example[, c(2,3)], data=example[,
c(1,4)], proj4string = CRS("+proj=longlat +ellps=WGS84")). 

>From the output I get (below), I deduce that creating this new object has
worked.

class       : SpatialPointsDataFrame 

features    : 130 

coord. ref. : +proj=longlat +ellps=WGS84 

variables   : 2

names       :       id,        timestamp 

min values  : 1st_trip, 15/10/2013 18:18 

max values  : 2nd_trip,  18/10/2013 6:54

 

 

When I try to use the kerneloverlap function however, I get an output that I
don't understand. 

 
kerneloverlap(example_df[,1], meth="HR")
          1st_trip 2nd_trip
1st_trip 1.0000000        1
2nd_trip 0.4895288        1

 

I am not sure why the results are not symmetrical (in one instance the
overlap between trip 1 and 2 is 1, in the other it is 0.4895288.). Trying
the first calculate the UD distribution with kernelUD and using the function
kerneloverlaphr to calculate the overlap yielded the same result. I thought
that would have fixed the problem as I read on the forums that inconsistent
output could come from the grid size changing from individual to individual
(or in my case trip to trip) but using the parameter same4all=TRUE and
conditional=TRUE for kerneloverlaphr did not provide a different result. 

Could someone let me know if I have made a mistake and how to fix it please?
Thanks in advance! 

Kind regards,

Elodie

 

Elodie Camprasse

6/187 Auburn Road

Hawthorn, VIC 3122

Australia 

 

Email:  <mailto:elodie.camprasse at gmail.com> elodie.camprasse at gmail.com

Website:  <http://hors-des-sentiers-battus.e-monsite.com/>
http://hors-des-sentiers-battus.e-monsite.com/

Mobile:  <tel:%28%2B61%29%20049%20794%200793> (+61) 049 794 0793 

 

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