burr: Burr distribution

In VaRES: Computes value at risk and expected shortfall for over 100 parametric distributions

Description

Computes the pdf, cdf, value at risk and expected shortfall for the Burr distribution due to Burr (1942) given by

\begin{array}{ll} &\displaystyle f (x) = \frac {b a^b}{x^{b + 1}} ≤ft[ 1 + ≤ft( x / a \right)^{-b} \right]^{-2}, \\ &\displaystyle F (x) = \frac {1}{1 + ≤ft( x / a \right)^{-b}}, \\ &\displaystyle {\rm VaR}_p (X) = a p^{1 / b} (1 - p)^{-1 / b}, \\ &\displaystyle {\rm ES}_p (X) = \frac {a}{p} B_p ≤ft( 1 / b + 1, 1 - 1 / b \right) \end{array}

for x > 0, 0 < p < 1, a > 0, the scale parameter, and b > 0, the shape parameter, where B_x (a, b) = \int_0^x t^{a - 1} (1 - t)^{b - 1} dt denotes the incomplete beta function.

Usage

dburr(x, a=1, b=1, log=FALSE)
pburr(x, a=1, b=1, log.p=FALSE, lower.tail=TRUE)
varburr(p, a=1, b=1, log.p=FALSE, lower.tail=TRUE)
esburr(p, a=1, b=1)

Arguments

x	scaler or vector of values at which the pdf or cdf needs to be computed
p	scaler or vector of values at which the value at risk or expected shortfall needs to be computed
a	the value of the scale parameter, must be positive, the default is 1
b	the value of the shape parameter, must be positive, the default is 1
log	if TRUE then log(pdf) are returned
log.p	if TRUE then log(cdf) are returned and quantiles are computed for exp(p)
lower.tail	if FALSE then 1-cdf are returned and quantiles are computed for 1-p

Value

An object of the same length as x, giving the pdf or cdf values computed at x or an object of the same length as p, giving the values at risk or expected shortfall computed at p.

Author(s)

Saralees Nadarajah

References

S. Nadarajah, S. Chan and E. Afuecheta, An R Package for value at risk and expected shortfall, submitted

Examples

x=runif(10,min=0,max=1)
dburr(x)
pburr(x)
varburr(x)
esburr(x)

VaRES documentation built on May 29, 2017, 8:27 p.m.