I got around my problem by using this version of the code:
mindistkeep2 <- function(x, threshold)
{
if (!inherits(x,"ltraj"))
stop("x should be of class 'ltraj'")
foo <- function(y) {
ul <- 1
if (nrow(y) > 2){######## skip for small burst
for (i in 2:nrow(y)) {
if(y$dist[i-1]<threshold){
ul[i]= ul[i-1]
y$dist[i] = sqrt( (y$x[i+1] -y$x
[ul[i]])*(y$x[i+1] -y$x [ul[i]])+(y$y[i+1]
-y$y [ul[i]])*(y$y[i+1] -y$y [ul[i]]) )##recalculate the distance from the first
point
} else ul[i]={i}
}
}
if (!is.null(attr(y, "infolocs"))) {
infol <- attr(y, "infolocs")
}
z <- y[ul,c("x","y")]
da <- y$date
if (!is.null(attr(y, "infolocs"))) {
infol <- attr(y, "infolocs")
lt <- as.ltraj(z, da, id=attr(y,"id"), burst=attr(y,"burst"),
typeII=attr(x,"typeII"), infolocs=infol)
} else {
lt <- as.ltraj(z, da, id=attr(y,"id"), burst=attr(y,"burst"),
typeII=attr(x,"typeII"))
}
return(lt)
}
res <- do.call("c.ltraj", lapply(x, foo))
class(res) <- c("ltraj","list")
return(res)
}
Feel free to add it (or a corrected version if there are mistakes) in the next
version of adehabitat (I also added a piece of code to avoid errors on very
short bursts).
thanks for all your work
julien
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