Distance-sampling detection functions and associated density functions
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)
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 |
distsamp for example of using these for plotting
detection function
# 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")Please choose more modern alternatives, such as Google Chrome or Mozilla Firefox.