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线性和二次插值
一剑行天下
posted @ 2008年11月01日 19:18
in 数值分析
, 2100 阅读
#include<stdio.h>
main()
{
float y1,y2,y3,x,x1,x2,x3;
float l1,l2,l3,y;
printf("下面是线性插值\n");
printf("input two points x1 ,x2,:\n因为求0.54点的值，所以选点0.5和0.6 input:\n");
scanf("%f,%f",&x1,&x2);
printf("请输入对应的函数值y1,y2\n");
scanf("%f,%f",&y1,&y2);
printf("input x=\n");
scanf("%f",&x);
l1=(x-x2)/(x1-x2);
l2=(x-x1)/(x2-x1);
y=y1*l1+y2*l2;
printf("线性插值结果y＝ln(%f)=%f\n",x,y);
printf("二次插值。请输入x1,x2,x3\n");
scanf("%f,%f,%f",&x1,&x2,&x3);
printf("input y1,y2,y3\n");
scanf("%f,%f,%f",&y1,&y2,&y3);
printf("input x=\n");
scanf("%f",&x);
l1=(x-x2)*(x-x3)/((x1-x2)*(x1-x3));
l2=(x-x1)*(x-x3)/((x2-x1)*(x2-x3));
l3=(x-x1)*(x-x2)/((x3-x1)*(x3-x2));
y=y1*l1+y2*l2+y3*l3;
printf("\n二次插值结果：ln(%f)=%f",x,y);
}
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