RTMBdist (version 0.1.0)

vmf2: Reparameterised von Mises-Fisher distribution

Description

Density, distribution function, and random generation for the von Mises-Fisher distribution.

Usage

dvmf2(x, theta, log = FALSE)
rvmf2(n, theta)

Value

dvmf gives the density and rvm generates random deviates.

Arguments

x

unit vector or matrix (with each row being a unit vector) of evaluation points

theta

direction and concentration vector. The direction of theta determines the mean direction on the sphere. The norm of theta is the concentration parameter of the distribution.

log

logical; if TRUE, densities are returned on the log scale.

n

number of random values to return.

Details

In this parameterisation, \(\theta = \kappa \mu\), where \(\mu\) is a unit vector and \(\kappa\) is the concentration parameter.

dvmf2 allows for automatic differentiation with RTMB. rvmf2 is imported from movMF::rmovMF.

Examples

set.seed(123)
# single parameter set
theta <- c(1,2,3)
x <- rvmf2(1, theta)
d <- dvmf2(x, theta)

# vectorised over parameters
theta <- matrix(theta, nrow = 1)
theta <- theta[rep(1,10), ]
x <- rvmf2(10, theta)
d <- dvmf2(x, theta)