[AniMov] R package ADEhabitatLT - function ltraj/cutltraj - bursts
Clement.Calenge at oncfs.gouv.fr
Thu Oct 9 15:41:51 CEST 2014
On 09/10/2014 15:36, Michael Sumner wrote:
> Would it not be ok to just interpolate a redundant point between the
> two? Then you don't fall foul of the rules?
yes, that would be a better solution (no need to edit the function then).
All the best,
> That seems safer and more reproducible than moving the ground under your feet?
> (Just my 2 cents having not tested either path).
> Cheers, Mike.
> On Thu, Oct 9, 2014 at 9:57 PM, Calenge Clement
> <Clement.Calenge at oncfs.gouv.fr> wrote:
>>> I have a question concerning the ADEhabitatLT package in R. We are
>>> analyzing GPS data of beavers sampled at an 15 min interval from approx.
>>> 7 pm - 7 am for 7 nights. The aim of our study is to look at changes in
>>> movement behavior after capture (we tag them with GPS units and release
>>> them afterwards).
>>> We used the ltraj function to create an ltraj object with bursts for
>>> every individual. We then divided the bursts into sub-bursts for every
>>> night with cutltraj by using time lags over 8 hrs (when beavers are
>>> inside the lodge during daytime) for splitting up. However, we get a
>>> warning message saying that
>>> Warning message:
>>> In cutltraj(Beav, "foo(dt)", nextr = TRUE) :
>>> At least 3 relocations are needed for a burst
>>> 9 relocations have been deleted
>>> For our purpose, the first night after capture is really important. And
>>> just for this night, we sometimes only got 2 relocations since the
>>> animals went into their lodge (no GPS signal), meaning that the function
>>> just deletes the first night for some of our animals. We thus would like
>>> to include these bursts for analysis and wonder whether there is a
>>> possibility to create a burst with only 2 relocations?
>> Some of the statistics used to describe the trajectory require at least
>> two steps, i.e. 3 relocations (e.g. the relative angle, or turning
>> angles, between successive steps). However, if you insist, you can edit
>> the function cutltraj, e.g. using the command:
>> and delete the following commands at the end of the function:
>> resb <- res[rrr >= 3]
>> if (length(res) != length(resb))
>> warning(paste("At least 3 relocations are needed for a burst\n",
>> sum(rrr[rrr < 3]), "relocations have been deleted"))
>> This will avoid this unwanted behaviour. However, I cannot guarantee
>> that the other functions in adehabitatLT will work with a 2-relocations
>> ltraj (Two relocations do not define a trajectory; you need at least
>> three). You are on your own if you decide to do that!
>> Clément Calenge
>> Clément CALENGE
>> Cellule d'appui à l'analyse de données
>> Direction des Etudes et de la Recherche
>> Office national de la chasse et de la faune sauvage
>> Saint Benoist - 78610 Auffargis
>> tel. (33) 01.30.46.54.14
>> AniMov mailing list
>> AniMov at faunalia.it
Cellule d'appui à l'analyse de données
Direction des Etudes et de la Recherche
Office national de la chasse et de la faune sauvage
Saint Benoist - 78610 Auffargis
tel. (33) 01.30.46.54.14
More information about the AniMov