8hmt0.c

来自「埃米尔插值在vc++中的实现」· C语言 代码 · 共 39 行

  #include "stdio.h"
  //给定n个节点的函数值及一阶导数用艾米尔特公式插值
  double hmt(x,y,dy,n,t)
  int n;
  double t,x[],y[],dy[];
  { int i,j;
    double z,p,q,s;
    z=0.0;
    for (i=1;i<=n;i++)
      { s=1.0;
        for (j=1;j<=n;j++)
          if (j!=i) s=s*(t-x[j-1])/(x[i-1]-x[j-1]);
        s=s*s;
        p=0.0;
        for (j=1;j<=n;j++)
          if (j!=i) p=p+1.0/(x[i-1]-x[j-1]);
        q=y[i-1]+(t-x[i-1])*(dy[i-1]-2.0*y[i-1]*p);
        z=z+q*s;
      }
    return(z);
  }


  main()
  { int i;
    double t,z;
    static double x[10]={0.1,0.15,0.3,0.45,0.55,0.6,0.7,0.85,0.9,1.0};
    static double y[10]={0.904837,0.860708,0.740818,0.637628,0.576950,
                       0.548812,0.496585,0.427415,0.406570,0.367879};
    static double dy[10];
    printf("\n");
    for (i=0;i<=9;i++) dy[i]=-y[i];
    t=0.356; z=hmt(x,y,dy,10,t);
    printf("t=%6.3f,   z=%e\n",t,z);
    printf("\n");
  }