Compute the distance between the trajectories of two animals with varying sampling intervals
As far as I can tell, there is no such function in adehabitatLT. However, I wrote a function 'closest' [1] in the package 'hab' [2], which specifically does that: find the closest relocations from ltraj objects. It can work with only one ltraj, in which case it will look in other bursts, or with two different ltraj, in which case it will in the other ltraj. Most importantly, you can define a temporal windows to restrict the search, which may solve your problem of irregular time (the ltraj do not have to be regular, or on the same time schedule). It's only Euclidean distance though. Lastly, it works at the location level, i.e. it's not considering lines (steps). If that's what you're looking for, I would probably suggest using PostGIS... Hope this helps, Mathieu. [1] https://github.com/basille/hab/blob/master/R/closest.r [2] https://github.com/basille/hab Le 22/07/2015 10:09, Jeremy Chacon a ?crit :
I bet Sarah's right and adehabitatLT has something, but I also know that the longitudinalData package can compute distances between two trajectories including the frechet distance. http://www.inside-r.org/packages/cran/longitudinalData/docs/pathFrechet However, it does not deal with the timing problem. You will have to roll your own method of aligning the trajectories in time. On Wed, Jul 22, 2015 at 9:02 AM, Sarah Goslee <sarah.goslee at gmail.com> wrote:
Try the adehabitatLT package. On Wed, Jul 22, 2015 at 9:41 AM, Andr? Zehnder <andrezehnder at hotmail.com> wrote:
Hi list, I want to compute the distances between two trajectories that consist of
a
sequence of point measurements. The trajectories do not have the same
length
or sampling interval. So, while for animal A, there is a data point at
15.00
p.m. and another at 15.38 p.m, animal B might have data points at 14.56
p.m.
and 17.02 p.m. A possible approach would be to connect these point series to
trajectories
and then calculate the distance between the two trajectories at the
sampled
positions of one trajectory (take the sampled position of the second trajectory that is temporally closest). Are there any packages in R (or tools outside of R) that allow me to do this? The support of other
distances
than the Euclidean one (e.g. Fr chet) would be an advantage. Best regards, Andre
-- Sarah Goslee http://www.functionaldiversity.org
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