Generalized Pareto mean and variance
[m,v] = gpstat(k,sigma,theta)
[m,v] = gpstat(k,sigma,theta)
returns the mean of and variance for the generalized Pareto (GP) distribution with the tail index (shape) parameterk
, scale parametersigma
, and threshold (location) parameter,theta
.
The default value fortheta
is 0.
Whenk = 0
andtheta = 0
, the GP is equivalent to the exponential distribution. Whenk > 0
andtheta = sigma/k
, the GP is equivalent to a Pareto distribution with a scale parameter equal tosigma/k
and a shape parameter equal to1/k
. The mean of the GP is not finite whenk
≥1
, and the variance is not finite whenk
≥1/2
. Whenk
≥0
, the GP has positive density forx > theta
, or when
k < 0
,
.
[1] Embrechts, P., C. Klüppelberg, and T. Mikosch.Modelling Extremal Events for Insurance and Finance. New York: Springer, 1997.
[2] Kotz, S., and S. Nadarajah.Extreme Value Distributions: Theory and Applications. London: Imperial College Press, 2000.