# SuanShu, a Java numerical and statistical library

com.numericalmethod.suanshu.analysis.function.special.gamma

## Class GammaRegularizedPInverse

• All Implemented Interfaces:
Function<Vector,Double>, BivariateRealFunction, RealScalarFunction

public class GammaRegularizedPInverse
extends AbstractBivariateRealFunction
The inverse of the Regularized Incomplete Gamma P function is defined as: $x = P^{-1}(s,u), 0 \geq u \geq 1$
• When s > 1, we use the asymptotic inversion method.
• When s <= 1, we use an approximation of P(s,x) together with a higher-order Newton like method.
In both cases, the estimated value is then improved using Halley's method, c.f., HalleyRoot.

The R equivalent function is qgamma. E.g., qgamma(u, s, lower=TRUE).

• ### Nested classes/interfaces inherited from interface com.numericalmethod.suanshu.analysis.function.Function

Function.EvaluationException
• ### Constructor Summary

Constructors
Constructor and Description
GammaRegularizedPInverse()
• ### Method Summary

All Methods
Modifier and Type Method and Description
double evaluate(double s, double u)
Evaluate x = P-1(s,u).
• ### Methods inherited from class com.numericalmethod.suanshu.analysis.function.rn2r1.AbstractBivariateRealFunction

evaluate
• ### Methods inherited from class com.numericalmethod.suanshu.analysis.function.rn2r1.AbstractRealScalarFunction

dimensionOfDomain, dimensionOfRange
• ### Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
• ### Methods inherited from interface com.numericalmethod.suanshu.analysis.function.Function

dimensionOfDomain, dimensionOfRange
• ### Constructor Detail

• #### GammaRegularizedPInverse

public GammaRegularizedPInverse()
• ### Method Detail

• #### evaluate

public double evaluate(double s,
double u)
Evaluate x = P-1(s,u).
Parameters:
s - s > 0
u - 0 ≤ u ≤ 1
Returns:
P-1(s,u)