angextrapo: Bivariate angular dependence function for extrapolation based on rays
Description
The scale parameter \(g(w)\) in the Ledford and Tawn approach is estimated empirically for
\(x\) large as $$\frac{\Pr(X_P>xw, Y_P>x(1-w))}{\Pr(X_P>x, Y_P>x)}$$
where the sample (\(X_P, Y_P\)) are observations on a common unit Pareto scale.
The coefficient \(\eta\) is estimated using maximum likelihood as the
shape parameter of a generalized Pareto distribution on \(\min(X_P, Y_P)\).