Would it not be ok to just interpolate a redundant point between the two? Then you don't fall foul of the rules?
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 <[email protected]> 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: > > cultraj<-edit(cutltraj) > > 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! > > HTH, > > 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 > [email protected] > http://lists.faunalia.it/cgi-bin/mailman/listinfo/animov -- Michael Sumner Software and Database Engineer Australian Antarctic Division Hobart, Australia e-mail: [email protected] _______________________________________________ AniMov mailing list [email protected] http://lists.faunalia.it/cgi-bin/mailman/listinfo/animov
