sigmaSEA {SIBER}

Calculate metrics corresponding to the Standard Ellipse based on a covariance matrix

Description

This function takes a covariance 2x2 matrix Sigma and returns various metrics relating to the corresponding Standard Ellipse. The function is limited to the 2-dimensional case, as many of the ancillary summary statistics are not defined for higher dimensions (e.g. eccentricity).

Usage

sigmaSEA(sigma)

Arguments

sigma

a 2x2 covariance ellipse.

Value

A list comprising the following metrics for summarising the Standard Ellipse

• SEA the Standard Ellipse Area (not sample size corrected).

• eccentricity a measure of the elongation of the ellipse.

• a the length of the semi-major axis.

• b the length of the semi-minor axis.

Note

This function is currently based on the eigenvalue and eigenvector approach which is more flexible for higher dimensional problems method for calculating the standard ellipse, and replaces the parametric method used previously in siar and siber.

Examples

# A perfect circle
sigma <- matrix( c(1, 0, 0, 1), 2, 2)
sigmaSEA(sigma)