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Runuran (version 0.40)

udt: UNU.RAN object for Student t distribution

Description

Create UNU.RAN object for a Student t distribution with with df degrees of freedom.

[Distribution] -- t (Student).

Usage

udt(df, lb=-Inf, ub=Inf)

Value

An object of class "unuran.cont".

Arguments

df

degrees of freedom (strictly positive). Non-integer values allowed.

lb

lower bound of (truncated) distribution.

ub

upper bound of (truncated) distribution.

Author

Josef Leydold and Wolfgang H\"ormann unuran@statmath.wu.ac.at.

Details

The \(t\) distribution with df \(= \nu\) degrees of freedom has density $$ f(x) = \frac{\Gamma ((\nu+1)/2)}{\sqrt{\pi \nu} \Gamma (\nu/2)} (1 + x^2/\nu)^{-(\nu+1)/2} $$ for all real \(x\). It has mean \(0\) (for \(\nu > 1\)) and variance \(\frac{\nu}{\nu-2}\) (for \(\nu > 2\)).

The domain of the distribution can be truncated to the interval (lb,ub).

References

N.L. Johnson, S. Kotz, and N. Balakrishnan (1995): Continuous Univariate Distributions, Volume 2. 2nd edition, John Wiley & Sons, Inc., New York. Chap. 28, p. 362.

See Also

unuran.cont.

Examples

Run this code
## Create distribution object for t distribution
distr <- udt(df=4)
## Generate generator object; use method PINV (inversion)
gen <- pinvd.new(distr)
## Draw a sample of size 100
x <- ur(gen,100)

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