quexiangercheng.java

数值分析之计算方法与实验5：曲线拟合 by java

import java.io.*;
class Quexiangercheng{				
	static int n=0,p=1;
	static int row=0,line=0;
	public static void main(String[] args)throws IOException{
  	PrintWriter out = new PrintWriter(new FileWriter("result.txt"));
		double[] x={1,2.5,3.5,4}; 
		double[] y={3.8,1.5,26,33};
		n=x.length;
		double[][] not=new double[p+1][n];
		not=findnot(x);//将not矩阵求出
		//将s矩阵求出
		double[][] s=new double[p+1][p+1];
		for(int i=0;i<=p;i++){
			for(int j=0;j<=i&&j<=p;j++){
				s[i][j]=neiji(not[i],not[j]);
				s[j][i]=s[i][j];
			}
		}
		double[] t=new double[p+1];
		for(int i=0;i<=p;i++){
			t[i]=neiji(y,not[i]);
			//System.out.print(t[i]+"   ");
		}
		double[][] ab=new double[p+1][p+2];
		for(int i=0;i<=p;i++){
			for(int j=0;j<=p;j++)ab[i][j]=s[i][j];
		}
		for(int i=0;i<=p;i++)ab[i][p+1]=t[i];
		row=p+1;line=p+2;
		double[] a=directLU(ab);
		out.println("计算结果:"+"\n"+"y="+a[0]+" + "+a[1]+"XX");				
	  out.close();
	  }
	static double neiji(double[] x,double[] y){
		double s=0;
		for(int i=0;i<x.length;i++)s+=x[i]*y[i];
		return s;
	}	
	static double[][] findnot(double[] x){
		double[][] not=new double[p+1][n];
		for(int j=0;j<n;j++){
			not[0][j]=Math.pow(x[j],0);
			not[1][j]=Math.pow(x[j],2);
		}
		return not;
	}
	static double[] directLU(double[][] ab){	//方法见前章
		double[][] u=new double[row][line];
		double[][] l=new double[row][row];
		for(int j=0;j<line;j++)u[0][j]=ab[0][j];
		for(int i=1;i<row;i++)l[i][0]=ab[i][0]/ab[0][0];
		for(int k=1;k<row;k++){
			for(int j=k;j<line;j++){
				u[k][j]=ab[k][j];
				for(int q=0;q<=k-1;q++){
					u[k][j]=u[k][j]-u[q][j]*l[k][q];
				}
			}
			for(int i=k+1;i<row;i++){
				l[i][k]=u[k][i]/u[k][k];
			}
		}
		double[] x=new double[row];
		x[row-1]=u[row-1][line-1]/u[row-1][line-2];
		for(int i=row-2;i>=0;i--){
			x[i]=u[i][line-1];
			for(int j=i+1;j<=line-2;j++){
				x[i]=x[i]-u[i][j]*x[j];
			}
			x[i]=x[i]/u[i][i];
		}
		return x;	
	}
}