xianxing.c

计算方法c线性插值函数

#include <stdio.h>
#include <stdlib.h>
#include <malloc.h>
double LIP(int n,double t,double *x,double *y)
{
    int i,j,k;
    double u,f;
    for(i=0;i<=n-2;i++)
    {
        if(t<=x[i+1])
        {
            k=i;
            break;
        }
        else
            k=n-2;
    }
    u=(t-x[k])/(x[k+1]-x[k]);
    f=y[k]+u*(y[k+1]-y[k]);
    return (f);
}
double LIP(int ,double,double*,double*);
main()
{
    unsigned i,n;
    double *x,*y,t,f;
    n=6;
    t=75.5;
    x=(double*)calloc(n,sizeof(double));
    if(x==NULL)
        exit(1);
    y=(double*)calloc(n,sizeof(double));
    if(y==NULL)
        exit(1);
    x[0]=75;
    x[1]=76;
    x[2]=77;
    x[3]=78;
    x[4]=79;
    x[5]=80;
    y[0]=2.768;
    y[1]=2.833;
    y[2]=2.903;
    y[3]=2.979;
    y[4]=3.062;
    y[5]=3.153;
    printf("使用线性插值算法:\n");
    printf("当x=75.7时,结果为 %f \n",LIP(n,t,x,y));
    t=78.3;
    printf("当x=78.3时,结果为 %f \n",LIP(n,t,x,y));
    free(x);
    free(y);
}