Detection PDFs

Detects specimens with decaying probability with > y, irregardless of x.

phnorm(x, y, theta)

Arguments

x	x-coordinates for specimens
y	y-coordinates for specimens
theta	mean parameter for half normal distribution

References

Clark RG (2016) Statistical Efficiency in Distance Sampling. PLoS ONE 11(3): e0149298. doi:10.1371/journal.pone.0149298