## java广义超几何函数内容来源于 Stack Overflow，并遵循CC BY-SA 3.0许可协议进行翻译与使用

• 回答 (2)
• 关注 (0)
• 查看 (69)

### 2 个回答

/**
* The generalized hypergeometric function is a convergent power series \sum_{i=0}^{\infty} c_i x^i
* where the coefficients satisfy c_{n+1}/c_n = A(n)/B(n) for some polynomials A and B in n.
* It is customary to factor out the leading term, so c_0 is assumed to be 1
*/

public class HypergeometricFunction {
private final int degreeOfApproximation;
private final double[] coefficientsOfA;
private final double[] coefficientsOfB;
private final double[] coefficientsOfHypergeometricFunction;

public HypergeometricFunction(int degreeOfApproximation, double[] coefficientsOfA, double[] coefficientsOfB) {
this.degreeOfApproximation = degreeOfApproximation;
this.coefficientsOfA = coefficientsOfA;
this.coefficientsOfB = coefficientsOfB;
this.coefficientsOfHypergeometricFunction = generateCoefficients();
}

/**
* @param x input
* @return Approximation to the hypergeometric function by taking the first
* {@code degreeOfApproximation} terms from the series.
*/
public double approximate(double x){
return evaluatePolynomial(x, coefficientsOfHypergeometricFunction);
}

private double[] generateCoefficients() {
double[] coefficients = new double[degreeOfApproximation];
coefficients[0] = 1;
for (int i = 1; i < degreeOfApproximation; i++)
coefficients[i] = (evaluatePolynomial(i, coefficientsOfA) / evaluatePolynomial(i, coefficientsOfB)) * coefficients[i - 1];
return coefficients;
}

private double evaluatePolynomial(double n, double[] coefficients) {
int length = coefficients.length;
double out = 0.0D;
for (int i = 0; i < length; i++) {
out += coefficients[i] * pow(n, i);
}
return out;
}

private double pow(double a, int b) {
double out = 1;
for (int i = 0; i < b; i++) out *= a;
return out;
}

}