Don: Doncaster's measure of dynamic interaction

Description

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 = 0, plot = TRUE)

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.

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.
plot: logical, whether or not to plot the Doncaster plot. Default = TRUE.

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.

References

Doncaster, C.P. (1992) Non-parametric estimates of interaction from radio-tracking data. Journal of Theoretical Biology, 143: 431-443.

Examples

Run this code

data(deer)
deer37 <- deer[1]
deer38 <- deer[2]
#tc = 7.5 minutes, dc = 50 meters
Don(deer37, deer38, tc = 7.5*60, dc = 50)

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