Density of the spherical ESAG and Kent distributions {Directional}

Density of the spherical ESAG and Kent distributions

Description

Density of the spherical ESAG and Kent distributions.

Usage

desag(y, mu, gam, logden = FALSE)
dkent(y, G, param, logden = FALSE )

Arguments

y

A matrix or a vector with the data expressed in Euclidean coordinates, i.e. unit vectors.

mu

The mean vector the ESAG distribution, a vector in R^3.

gam

The two \gamma parameters of the ESAG distribution.

G

For the Kent distribution only, a 3 x 3 matrix whose first column is the mean direction. The second and third columns are the major and minor axes respectively.

param

For the Kent distribution a vector with the concentration \kappa and ovalness \beta parameters. The \psi has been absorbed inside the matrix G.

logden

If you the logarithm of the density values set this to TRUE.

Details

The density of the spherical ESAG or Kent distribution is computed.

Value

A vector with the (log) density values of y.

Author(s)

Michail Tsagris.

R implementation and documentation: Michail Tsagris [e-mail].

References

Mardia K. V. and Jupp P. E. (2000). Directional statistics. Chicester: John Wiley & Sons.

Paine P.J., Preston S.P., Tsagris M. and Wood A.T.A. (2018). An Elliptically Symmetric Angular Gaussian Distribution. Statistics and Computing, 28(3):689–697.

Kent John (1982). The Fisher-Bingham distribution on the sphere. Journal of the Royal Statistical Society, Series B, 44(1): 71–80.

See Also

kent.mle, rkent, esag.mle

Examples

m <- colMeans( as.matrix( iris[,1:3] ) )
y <- rkent(1000, k = 10, m = m, b = 4)
mod <- kent.mle(y)
dkent( y, G = mod$G, param = mod$param )