PROGRAM FOR INVERSE INTERPOLATION METHOD IN C PROGRAMMING.

#include<stdio.h>

#include<conio.h>

#define MAX 10

void main()

{

    FILE *fp;

    int number,i,j;

    float xvalue[MAX],yvalue[MAX],search,product;

    float sum=0;

    fp=fopen("lgrninv.dat","w");

    clrscr();

    printf("\n\n");

    fprintf(fp,"\n\n");

    printf("How many numbers you want to enter for x  : ");

    fprintf(fp,"How many numbers you want to enter for x  : ");

    scanf("%d",&number);

    fprintf(fp,"%d",number);

    for(i=0;i<number;i++)

    {

        printf("\nEnter value for x(%d)  : ",i);

        fprintf(fp,"\nEnter value for x(%d)  : ",i);

        scanf("%f",&xvalue[i]);

        fprintf(fp,"%f",xvalue[i]);

        printf("\nEnter value for y(%d)  : ",i);

        fprintf(fp,"\nEnter value for y(%d)  : ",i);

        scanf("%f",&yvalue[i]);

        fprintf(fp,"%f",yvalue[i]);

    }

    printf("\nEnter y for which you want to find x :");

   fprintf(fp,"\nEnter y for which you want to find x:");

    scanf("%f",&search);

    fprintf(fp,"%f",search);

    for(i=0;i<number;i++)

    {

      product=1;

      for(j=0;j<number;j++)

      {

       if(i!=j)

       {

       product=product*(search-yvalue[j])/(yvalue[i]-yvalue[j]);

       }

      }

        sum=sum+xvalue[i]*product;

    }

    clrscr();

    printf("\n\n\n\n");

    fprintf(fp,"\n\n\n\n");

    printf("LAGRANGE'S INVERSE INTERPOLATION METHOD  ");

    fprintf(fp,"LAGRANGE'S INVERSE INTERPOLATION METHOD");

    printf("\n\n");

    fprintf(fp,"\n\n");

    printf("  X      Y   ");

    fprintf(fp,"  X      Y   ");

    printf("\n\n");

    fprintf(fp,"\n\n");

    for(i=0;i<number;i++)

    {

        printf("  %.2f  %.2f ",xvalue[i],yvalue[i]);

        fprintf(fp,"  %.2f %.2f ",xvalue[i],yvalue[i]);

        printf("\n");

        fprintf(fp,"\n");

    }

    printf("\n\n");

    fprintf(fp,"\n\n");

    printf("Interpolated value is  :   %.4f  ",sum);

    fprintf(fp,"Interpolated value is  :   %.4f  ",sum);

    fclose(fp);

    getch();

}