sampleMovement {SiMRiv}

Resample a simulated movement and compute step-wise statistics

Description

Resamples a movement simulated with the function simulate to a lower temporal resolution (frequency). Simultaneously, computes step length, turning angles (Turchin 1998) and accumulated resistance for each resampled step, assuming that a straight line connects each re-sampled location.

Usage

  sampleMovement(relocs, resolution = 1, resist = NULL)

Arguments

relocs

the simulated movement, an object returned by simulate. NOTE: currently this is only implemented for simulations of single individuals.

resolution

movement will be resampled every this number of time ticks. If 1, no resampling is done (but metrics are computed).

resist

a landscape resistance raster, usually the same that was used in simulate

Details

This function mimics what happens in real world movement data: it resamples the simulated movement (which is supposed to be infinitesimal) into a lower temporal resolution, so that it is comparable to real world field data (e.g. telemetry data). During the process, it computes, for each resampled step:

• the step length

• the turning angle

• the accumulated resistance along the step, assuming a straight line is taken from start to end

Value

A list with the components relocs and stats.

relocs contains the resampled positions, stats contains the metrics for each step (which has N-2 rows because of the turning angles).

Note

These metrics are only meaningful for resolution >> 1, otherwise they are just a consequence of the simulation input parameters.

References

• Turchin, P. 1998. Quantitative analysis of movement: measuring and modeling population redistribution in animals and plants (Vol. 1). Sinauer Associates, Sunderland, MA.

See Also

simulate.

Examples

library(SiMRiv)

LevyWalker <- species(
  state.RW() + state.CRW(0.99),
  trans = transitionMatrix(0.005, 0.02))

sim <- simulate(LevyWalker, 10000)
resamp <- sampleMovement(sim, 50)
plot(sim, type="l", asp=1, col = "#777777")
lines(resamp$relocs, col = "red")