The function Don measures the dynamic interaction between two moving objects following
the methods outlined by Doncaster (1990).
Usage
Don(traj1, traj2, tc = 0, dc = 50)
Arguments
traj1
an object of the class ltraj which contains the time-stamped
movement fixes of the first object. Note this object must be a type II
ltraj object. For more information on objects of this type see
help(ltraj).
traj2
same as traj1.
tc
time threshold for determining simultaneous fixes – see function: GetSimultaneous.
dc
distance tolerance limit (in appropriate units) for defining when
two fixes are spatially together.
Details
This function can be used to compute the Doncaster (1990) methods for measuring
dynamic interaction between two objects. The Doncaster method tests the proportion
of simultaneous fixes that are below dc against that which would be
expected based on the distribution of distances between all fixes.
Value
This function first returns a plot, for distance values ranging from 0 to the maximum
distance separating two fixes, of the observed proportion of simultaneous fixes below
each distance value. The expected values based on all fixes are also included.
Second, a list is returned that contains the contingency table of simultaneous fixes
(paired) and non-paired fixes below and above dc, along with the
associated p-value from the Chi-squared test.
conTable – contingency table showing frequency of paired and non-paired fixes above and below dc.
p.value – p-value from the Chi-squared test of conTable.
References
Doncaster, C.P. (1992) Non-parametric estimates of interaction from radio-tracking
data. Journal of Theoretical Biology, 143: 431-443.