拉格朗日插值法实验报告

1、拉格朗日插值法实验报告一、实验目的1、学习和掌握拉格朗日插值多项式。2、运用拉格朗日插值多项式进行计算。二、算法步骤函数定义double lgrr（int n,double X）输入所求节点x和已知的节点数n输出插值结果s步骤：1、输入 n 对数（xi，yi）（ i=0-n）2、令 s=03、对于 i=0-n T=yi对 j=0- n 但 j! = i T=T*(X-xj)/(xi-xj)令 s=s+T4、输出结果三流程图四、原程序#include main()(double X;int n;double lgrr(int n,double X);printf(input the aim nu

2、mberX);printf(input the number of pairs of numbers n:);scanf(%lf%d,&X,&n);lgrr(n,X);return 0;double lgrr(int n,double X)(double s=0,t;double x81,y81;int i,j;printf(input n pairs of numbers:n);for(i=0;in;i+)scanf(%lf%lf,&xi,&yi);for(i=0;in;i+)(t=yi;for(j=0;jn;j+)(if(j! = i)t=t*(X-xj)/(xi-xj);s=s+t;pr

3、intf(s=%fn,s);return 0;作业用程序#includemain()(double X;int n;double lgrr(int n,double X);printf(input the aim numberX);printf(input the number of pairs of numbers n:);scanf(%lf%d,&X,&n);lgrr(n,X);return 0;double lgrr(int n,double X)(FILE *fp;double s=0,t,z;double x81,y81;int i,j,k;if(fp=fopen(lgrr,txt,

4、r+)=NULL) printf(can not open the file.); printf(input n pairs of numbers:n);for(i=0;in;i+)scanf(%lf%lf,&xi,&yi);for(k=0;k=20;k+)(for(i=0;in;i+)(z=X+.01*k;t=yi;for(j=0;jn;j+)(if(j! = i)t=t*(z-xj)/(xi-xj);s=s+t;printf(s=%fn,s);fprintf(fp,s=%fn,s);return 0;五、作业：3-27s=0.198670s=0.407105s=0.625307s=0.853266s=1.090966s=1.338384s=1.595493s=1.862263s=2.138663s=2.424661s=2.720224s=3.025321s=3.339921s=3.663993s=