d2r9.cpp

二元拉格朗日插值方法

# include<iostream.h>
# include<math.h>
# include<iomanip.h>

void main() 
{
    //program d2r9
    //driver for routine polin2
    int n,i,j;
	double pi,x1,x2,f,dy,y,x1a[6],x2a[6],ya[6][6];
    n = 5;
    pi = 3.141593;
    for (i = 1; i<= n; i++)
	{
        x1a[i] = i * pi / n;
        for (j = 1 ;j<= n;j++)
		{
            x2a[j] = 1.0* j / n;
            ya[i][j] = sin(x1a[i]) * exp(x2a[j]);
        }
    }
    //test 2-dimensional interpolation
    cout<<endl;
    cout<<"       x1        x2        f[x]   interpolated  error"<<endl;
    for (i = 1; i<= 4; i++)
	{
        x1 = (-0.1 + i / 5.0) * pi;
        for (j = 1; j<= 4; j++)
		{
            x2 = -0.1 + j / 5.0;
            f = sin(x1) * exp(x2);
            polin2(x1a, x2a, ya, n, n, x1, x2, y, dy);
			cout<<setprecision(6)<<setiosflags(ios::fixed);
            cout<<setw(11)<<x1;
            cout<< setw(11)<<x2;
            cout<< setw(11)<<f;
            cout<< setw(11)<<y;
            cout<< setw(11)<<dy<<endl;
        }
        cout<<"**********************************"<<endl;
    }
}