Hi, 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? We do see that it's not possible to calculate turning angles by using only 2 reloc, but we would like to include "time active" and maybe distance for our analysis. This is the code we use xy <- coordinates(GPSbeaver1 [,c("x","y")]) Beav <- as.ltraj(xy = GPSbeaver1[,c("x", "y")], date=GPSbeaver1$localtime, id=GPSbeaver1$ID, infolocs=GPSbeaver1[,c(2:4,9:10)]) head(Beav) head(Beav[[1]]) Beav1 <- ld(Beav) # creates a dataframe of all datapoints head(Beav1) is.regular(Beav) foo <- function(dt) { return(dt> (3600*8)) } Beav2 <- cutltraj(Beav, "foo(dt)", nextr = TRUE) head(Beav2) Thanks a lot for your time! All the best, aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa Patricia
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