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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