Contour plot (on the sphere) of the ESAG and Kent distributions {Directional}

Contour plot (on the sphere) of the ESAG and Kent distributions

Description

The contour plot (on the sphere) of the ESAG and Kent distributions is produced.

Usage

spher.esag.contour(mu, gam, bgcol = "snow", dat = NULL, col = NULL,
lat = 50, long = 50)
spher.kent.contour(G, param, bgcol = "snow", dat = NULL, col = NULL,
lat = 50, long = 50)

Arguments

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, 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 angle \psi has been absorbed inside the matrix G.

bgcol

The color of the surface of the sphere.

dat

If you have you want to plot supply them here. This has to be a numerical matrix with three columns, i.e. unit vectors.

col

If you supplied data then choose the color of the points. If you did not choose a color, the points will appear in red.

lat

A positive number determing the range of degrees to move left and right from the latitude center. See the example to better understand this argument.

long

A positive number determing the range of degrees to move up and down from the longitude center. See the example to better understand this argument.

Details

The goal of this function is for the user to see how the ESAG or the Kent distribution looks like.

Value

A plot containing the contours of the distribution.

Author(s)

Michail Tsagris.

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

References

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

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.

See Also

esag.contour, spher.purka.contour, kent.contour

Examples

mu <- colMeans( as.matrix( iris[, 1:3] ) )
gam <- c(1 ,0.5)
## the lat and long are decreased to 30. Increase them back to 50 to
## see the difference
spher.esag.contour(mu, gam, lat = 30, long = 30)