ch4_1.java

Java环境下实现的数值分析程序

class ch4_1{
	static double Lagrange(double[] x,double [] y,double x0,int m){
		double L=0.0;
		double []a=new double[m];
		for(int k=0;k<m;k++)a[k]=0.0;
		for(int i=0;i<m;i++){
			a[i]=y[i];
			for(int j=0;j<m;j++){
				if(j==i)continue;
				a[i]*=(x0-x[j])/(x[i]-x[j]);
			}
			L+=a[i];
		}
		return L;
	}
	public static void main(String [] args){
		int m=3;
		double [] x1={-3.0,-1.0,1.0};
		double [] y1={1.0,1.5,2.0};
		double [] x2={-1.0,1.0,2.0};
		double [] y2={1.5,2.0,2.0};
		double [] x3={1.0,2.0,3.0};
		double [] y3={2.0,2.0,1.0};
		double x10=-2.0; 
		double x20=0.0;
		double x30=2.75;
		System.out.println("x1="+x10+" y1="+Lagrange(x1,y1,x10,m));
		System.out.println("x2="+x20+" y2="+Lagrange(x2,y2,x20,m));
		System.out.println("x3="+x30+" y3="+Lagrange(x3,y3,x30,m));
	}
}