Gamma: Gamma Distribution

In Distributacalcul: Probability Distribution Functions

Description

Gamma distribution with shape parameter alpha and rate parameter beta.

Usage

expValGamma(shape, rate = 1/scale, scale = 1/rate)

varGamma(shape, rate = 1/scale, scale = 1/rate)

kthMomentGamma(k, shape, rate = 1/scale, scale = 1/rate)

expValLimGamma(d, shape, rate = 1/scale, scale = 1/rate)

expValTruncGamma(d, shape, rate = 1/scale, scale = 1/rate, less.than.d = TRUE)

stopLossGamma(d, shape, rate = 1/scale, scale = 1/rate)

meanExcessGamma(d, shape, rate = 1/scale, scale = 1/rate)

VatRGamma(kap, shape, rate = 1/scale, scale = 1/rate)

TVatRGamma(kap, shape, rate = 1/scale, scale = 1/rate)

mgfGamma(t, shape, rate = 1/scale, scale = 1/rate)

Arguments

shape	shape parameter alpha, must be positive.
rate	rate parameter beta, must be positive.
scale	alternative parameterization to the rate parameter, scale = 1 / rate.
k	kth-moment.
d	cut-off value.
less.than.d	logical; if TRUE (default) truncated mean for values <= d, otherwise, for values > d.
kap	probability.
t	t.

Details

The Gamma distribution with shape parameter a and rate parameter b has density:

f(x) = b^a / Γ(a) x^{a - 1} e^{-b x}

for x > 0, b, a > 0.

Value

Function :

• expValGamma gives the expected value.

• varGamma gives the variance.

• kthMomentGamma gives the kth moment.

• expValLimGamma gives the limited mean.

• expValTruncGamma gives the truncated mean.

• stopLossGamma gives the stop-loss.

• meanExcessGamma gives the mean excess loss.

• VatRGamma gives the Value-at-Risk.

• TVatRGamma gives the Tail Value-at-Risk.

• mgfGamma gives the moment generating function (MGF).

Invalid parameter values will return an error detailing which parameter is problematic.

Note

Function VatRGamma is a wrapper for the qgamma function stats package.

Examples

# With scale parameter
expValGamma(shape = 3, scale = 4)

# With rate parameter
expValGamma(shape = 3, rate = 0.25)


# With scale parameter
varGamma(shape = 3, scale = 4)

# With rate parameter
varGamma(shape = 3, rate = 0.25)


# With scale parameter
kthMomentGamma(k = 2, shape = 3, scale = 4)

# With rate parameter
kthMomentGamma(k = 2, shape = 3, rate = 0.25)


# With scale parameter
expValLimGamma(d = 2, shape = 3, scale = 4)

# With rate parameter
expValLimGamma(d = 2, shape = 3, rate = 0.25)


# With scale parameter
expValTruncGamma(d = 2, shape = 3, scale = 4)

# With rate parameter
expValTruncGamma(d = 2, shape = 3, rate = 0.25)

# values greather than d
expValTruncGamma(d = 2, shape = 3, rate = 0.25, less.than.d = FALSE)


# With scale parameter
stopLossGamma(d = 2, shape = 3, scale = 4)

# With rate parameter
stopLossGamma(d = 2, shape = 3, rate = 0.25)


# With scale parameter
meanExcessGamma(d = 2, shape = 3, scale = 4)

# With rate parameter
meanExcessGamma(d = 2, shape = 3, rate = 0.25)


# With scale parameter
VatRGamma(kap = .2, shape = 3, scale = 4)

# With rate parameter
VatRGamma(kap = .2, shape = 3, rate = 0.25)


# With scale parameter
TVatRGamma(kap = .2, shape = 3, scale = 4)

# With rate parameter
TVatRGamma(kap = .2, shape = 3, rate = 0.25)


mgfGamma(t = 1, shape = 3, rate = 5)

Distributacalcul documentation built on Sept. 13, 2020, 5:19 p.m.