Class ChiSquaredDistribution

java.lang.Object
cloud.opencode.base.math.distribution.ChiSquaredDistribution
public final class ChiSquaredDistribution extends Object
Immutable chi-squared distribution. 不可变卡方分布

Provides PDF, CDF, and inverse CDF (quantile function). Thread-safe: instances are immutable.

提供概率密度函数、累积分布函数和逆累积分布函数（分位函数）。 线程安全：实例不可变。

Since:
JDK 25, opencode-base-math V1.0.3
Author:
Leon Soo www.LeonSoo.com
See Also:

  • Method Details

    • of

      public static ChiSquaredDistribution of(double degreesOfFreedom)
      Creates a chi-squared distribution with the specified degrees of freedom. 创建具有指定自由度的卡方分布
      Parameters:
      degreesOfFreedom - the degrees of freedom, must be > 0 / 自由度，必须 > 0
      Returns:
      a new ChiSquaredDistribution instance / 新的卡方分布实例
      Throws:
      IllegalArgumentException - if degreesOfFreedom ≤ 0 or is not finite

    • degreesOfFreedom

      public double degreesOfFreedom()
      Returns the degrees of freedom. 返回自由度
      Returns:
      the degrees of freedom / 自由度

    • pdf

      public double pdf(double x)
      Computes the probability density function (PDF) at x. 计算在 x 处的概率密度函数值

      f(x) = x^(df/2-1) * exp(-x/2) / (2^(df/2) * Gamma(df/2))

      Parameters:
      x - the point at which to evaluate the PDF / 计算 PDF 的点
      Returns:
      the density at x / x 处的密度值

    • cdf

      public double cdf(double x)
      Computes the cumulative distribution function (CDF) at x. 计算在 x 处的累积分布函数值

      F(x) = P(df/2, x/2) where P is the regularized lower incomplete gamma function.

      Parameters:
      x - the point at which to evaluate the CDF / 计算 CDF 的点
      Returns:
      the cumulative probability P(X ≤ x) / 累积概率

    • inverseCdf

      public double inverseCdf(double p)
      Computes the inverse CDF (quantile function). 计算逆累积分布函数（分位函数）
      Parameters:
      p - the cumulative probability, must be in (0, 1) / 累积概率，必须在 (0, 1) 内
      Returns:
      the quantile x such that P(X ≤ x) = p / 使得 P(X ≤ x) = p 的分位数
      Throws:
      MathException - if p is not in (0, 1)

    • toString

      public String toString()
      Overrides:
      toString in class Object