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.campra...@gmail.com> elodie.campra...@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
reproducible_example_kerneloverlap.csv
Description: MS-Excel spreadsheet
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