detFuns: Distance-sampling detection functions and associated density...

In ianfiske/unmarked: Models for Data from Unmarked Animals

Description

These functions represent the currently available detection functions used for modeling line and point transect data with distsamp. Detection functions begin with "g", and density functions begin with a "d".

Usage

gxhn(x, sigma)
gxexp(x, rate)
gxhaz(x, shape, scale)

dxhn(x, sigma)
dxexp(x, rate)
dxhaz(x, shape, scale)
drhn(r, sigma)
drexp(r, rate)
drhaz(r, shape, scale)

Arguments

x	Perpendicular distance
r	Radial distance
sigma	Shape parameter of half-normal detection function
rate	Shape parameter of negative-exponential detection function
shape	Shape parameter of hazard-rate detection function
scale	Scale parameter of hazard-rate detection function

See Also

distsamp for example of using these for plotting detection function

Examples

# Detection probabilities at 25m for range of half-normal sigma values.
round(gxhn(25, 10:15), 2)

# Plot negative exponential distributions
plot(function(x) gxexp(x, rate=10), 0, 50, xlab="distance", 
    ylab="Detection probability")
plot(function(x) gxexp(x, rate=20), 0, 50, add=TRUE, lty=2)
plot(function(x) gxexp(x, rate=30), 0, 50, add=TRUE, lty=3)

# Plot half-normal probability density functions for line- and point-transects
par(mfrow=c(2, 1))
plot(function(x) dxhn(x, 20), 0, 50, xlab="distance", 
    ylab="Probability density", main="Line-transect")
plot(function(x) drhn(x, 20), 0, 50, xlab="distance", 
    ylab="Probability density", main="Point-transect")

ianfiske/unmarked documentation built on May 18, 2019, 1:28 a.m.