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mev (version 1.17)

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 \(\min(X_P, Y_P)\).

Usage

angextrapo(dat, qu = 0.95, w = seq(0.05, 0.95, length = 20))

Value

a list with elements

  • w: angles between zero and one

  • g: scale function at a given value of w

  • eta: Ledford and Tawn tail dependence coefficient

Arguments

dat

an \(n\) by \(2\) matrix of multivariate observations

qu

quantile level on uniform scale at which to threshold data. Default to 0.95

w

vector of unique angles between 0 and 1 at which to evaluate scale empirically.

References

Ledford, A.W. and J. A. Tawn (1996), Statistics for near independence in multivariate extreme values. Biometrika, 83(1), 169--187.

Examples

Run this code
angextrapo(rmev(n = 1000, model = 'log', d = 2, param = 0.5))

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