我需要找到一个(近似的、数值的)勒让德多项式的解。我尝试了几个Java库,但没有找到我需要的(最接近的是commons-math,甚至有用于在Laguerre求解器中找到解的代码,但它没有公开方法)。是否存在现成的解决方案,或者我需要自己实现?
我需要找到一个(近似的、数值的)勒让德多项式的解。我尝试了几个Java库,但没有找到我需要的(最接近的是commons-math,甚至有用于在Laguerre求解器中找到解的代码,但它没有公开方法)。是否存在现成的解决方案,或者我需要自己实现?
public class PolynomialRootFinder {
/**
* <p>
* Given a set of polynomial coefficients, compute the roots of the polynomial. Depending on
* the polynomial being considered the roots may contain complex number. When complex numbers are
* present they will come in pairs of complex conjugates.
* </p>
*
* @param coefficients Coefficients of the polynomial.
* @return The roots of the polynomial
*/
public static Complex64F[] findRoots(double... coefficients) {
int N = coefficients.length-1;
// Construct the companion matrix
DenseMatrix64F c = new DenseMatrix64F(N,N);
double a = coefficients[N];
for( int i = 0; i < N; i++ ) {
c.set(i,N-1,-coefficients[i]/a);
}
for( int i = 1; i < N; i++ ) {
c.set(i,i-1,1);
}
// Use generalized eigenvalue decomposition to find the roots
EigenDecomposition<DenseMatrix64F> evd = DecompositionFactory.eigGeneral(N, false);
evd.decompose(c);
Complex64F[] roots = new Complex64F[N];
for( int i = 0; i < N; i++ ) {
roots[i] = evd.getEigenvalue(i);
}
return roots;
}
}
eigGeneral
方法现在更改为eig
。 - zygimantusCommons-Math 对于多项式有一个合理的 API:
// -4 + 3 x + x^2
PolynomialFunction polynomial = new PolynomialFunction(new double[]{ -4, 3, 1});
LaguerreSolver laguerreSolver = new LaguerreSolver();
double root = laguerreSolver.solve(100, polynomial, -100, 100);
System.out.println("root = " + root);