d <- data.frame(x=1:10, y=rnorm(10), tms=Sys.time() + 1:10, id=gl(2, 5))
tr <- trip(d, c("tms", "id"))
## the method knows this is a trip, so there is a distance for every
## point, including 0s as the start and at transitions between
## individual trips
trackDistance(tr)
## the default method does not know about the trips, so this is
##(n-1) distances between all points
trackDistance(coordinates(tr), longlat = FALSE)
## we get NA at the start, end and at transitions between trips
angles <- trackAngle(tr)
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