pargpa {lmomco}R Documentation

Estimate the Parameters of the Generalized Pareto Distribution

Description

This function estimates the parameters of the Generalized Pareto distribution given the L-moments of the data in an ordinary L-moment object (lmom.ub or a trimmed L-moment object (TLmoms for t=1. The relation between distribution parameters and L-moments is seen under lmomgpa or lmomgpa2.

Usage

pargpa(lmom,zeta=1,xi=NULL,checklmom=TRUE)

Arguments

lmom A L-moment object created by lmom.ub, pwm2lmom, or TLmoms with trim=0.
zeta The right censoring fraction. If less than unity then a dispatch to the pargpaRC is made and the lmom argument must contain the B-type L-moments. If the data is not right, then this value must be left alone to the default of unity.
xi The lower limit of the distribution. If xi is known then alternative algorithms are used.
checklmom Should the lmom be checked for validity using the are.lmom.valid function. Normally this should be left as the default and it is very unlikely that the L-moments will not be viable (particularly in the tau_4 and tau_3 inequality). However, for some circumstances or large simulation exercises then one might want to bypass this check.

Value

An R list is returned.

type The type of distribution: gpa.
para The parameters of the distribution.
source The source of the parameters: “pargpa”.

Author(s)

W.H. Asquith

References

Hosking, J.R.M., 1990, L-moments—Analysis and estimation of distributions using linear combinations of order statistics: Journal of the Royal Statistical Society, Series B, vol. 52, p. 105–124.

Hosking, J.R.M., 1996, FORTRAN routines for use with the method of L-moments: Version 3, IBM Research Report RC20525, T.J. Watson Research Center, Yorktown Heights, New York.

Hosking, J.R.M. and Wallis, J.R., 1997, Regional frequency analysis—An approach based on L-moments: Cambridge University Press.

See Also

lmom.ub, lmomgpa, cdfgpa, quagpa

Examples

X   <- rexp(200)
lmr <- lmom.ub(X)
P1  <- pargpa(lmr)
P2  <- pargpa(lmr, xi=0.25)

## Not run: 
F <- nonexceeds()
plot(pp(X), sort(X))
lines(F,quagpa(F,P1))  # black line
lines(F, quagpa(F,P2), col=2)   # red line
## End(Not run)


[Package lmomco version 0.96.3 Index]