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".
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)
Perpendicular distance
Radial distance
Shape parameter of half-normal detection function
Shape parameter of negative-exponential detection function
Shape parameter of hazard-rate detection function
Scale parameter of hazard-rate detection function
distsamp
for example of using these for plotting
detection function
# NOT RUN {
# 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")
# }
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