geninvbeta function

Generalized inverse beta distribution

Computes the pdf, cdf, value at risk and expected shortfall for the generalized inverse beta distribution given by [REMOVE_ME]$\begin{array}{ll}&\displaystylef (x) = \frac {a x^{ac - 1}}{B (c, d) \left( 1 + x^a \right)^{c + d}},\\&\displaystyleF (x) = I_{\frac {x^a}{1 + x^a}} (c, d),\\&\displaystyle{\rm VaR}_p (X) = \left[ \frac {I_p^{-1} (c, d)}{1 - I_p^{-1} (c, d)} \right]^{1/a},\\&\displaystyle{\rm ES}_p (X) = \frac {1}{p} \int_0^p \left[ \frac {I_v^{-1} (c, d)}{1 - I_v^{-1} (c, d)} \right]^{1/a} dv\end{array} [REMOVE_ME_2]$

for $x > 0$, $0 < p < 1$, $a > 0$, the first shape parameter, $c > 0$, the second shape parameter, and $d > 0$, the third shape parameter.

Description

Computes the pdf, cdf, value at risk and expected shortfall for the generalized inverse beta distribution given by

for $x > 0$, $0 < p < 1$, $a > 0$, the first shape parameter, $c > 0$, the second shape parameter, and $d > 0$, the third shape parameter.

dgeninvbeta(x, a=1, c=1, d=1, log=FALSE)
pgeninvbeta(x, a=1, c=1, d=1, log.p=FALSE, lower.tail=TRUE)
vargeninvbeta(p, a=1, c=1, d=1, log.p=FALSE, lower.tail=TRUE)
esgeninvbeta(p, a=1, c=1, d=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 first shape parameter, must be positive, the default is 1
• c: the value of the second shape parameter, must be positive, the default is 1
• d: the value of the second 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

Returns

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.

References

Stephen Chan, Saralees Nadarajah & Emmanuel Afuecheta (2016). An R Package for Value at Risk and Expected Shortfall, Communications in Statistics - Simulation and Computation, 45:9, 3416-3434, tools:::Rd_expr_doi("10.1080/03610918.2014.944658")

Author(s)

Saralees Nadarajah

Examples

x=runif(10,min=0,max=1)
dgeninvbeta(x)
pgeninvbeta(x)
vargeninvbeta(x)
esgeninvbeta(x)