You cannot select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
59 lines
1.8 KiB
C++
59 lines
1.8 KiB
C++
|
|
|
|
/*----------------- LAGRANGE'S INTERPOLATION METHOD --------------------*/
|
|
|
|
/* THE PROGRAM CALCULATES THE VALUE OF f(x) AT GIVEN VALUE OF x
|
|
USING LAGRANGE'S INTERPOLATION METHOD.
|
|
|
|
INPUTS : 1) Number of entries of the data.
|
|
|
|
2) Values of 'x' & corresponding y = f(x).
|
|
|
|
3) Value of 'xr' at which y = f(x) to be calculated.
|
|
|
|
OUTPUTS : Interpolated value f(x) at x = xr. */
|
|
|
|
/*------------------------------ PROGRAM ----------------------------*/
|
|
|
|
#include<stdio.h>
|
|
#include<math.h>
|
|
#include<stdlib.h>
|
|
#include<conio.h>
|
|
|
|
void main()
|
|
{
|
|
double y[20],x[20],xr,fy,num,den;
|
|
int i,j,n;
|
|
clrscr();
|
|
printf("\n LAGRANGE'S INTERPOLATION TECHNIQUE");
|
|
printf("\n\nEnter the number of entries (max 20) = ");
|
|
/* ENTER THE NUMBER OF ENTRIES */
|
|
scanf("%d",&n);
|
|
for(i = 0; i < n; i++)
|
|
{
|
|
/* LOOP TO GET x AND y = f(x) IN THE ARRAY */
|
|
printf("x%d = ",i);
|
|
scanf("%lf",&x[i]);
|
|
printf(" y%d = ",i);
|
|
scanf("%lf",&y[i]);
|
|
}
|
|
printf("\nEnter the value of xr at which y = f(x)\n\t\t\t"
|
|
"is to be interpolated, xr = ");
|
|
scanf("%lf",&xr);
|
|
fy = 0;
|
|
for(j = 0; j < n; j++)
|
|
{
|
|
/* LOOP TO CALCULATE LAGRANGE'S INTERPOLATION */
|
|
num = den = 1;
|
|
for(i = 0; i < n; i++)
|
|
{
|
|
if(i == j) continue;
|
|
num = num * (xr - x[i]);
|
|
den = den * (x[j] - x[i]);
|
|
}
|
|
fy = fy + ((num/den) * y[j]);
|
|
}
|
|
printf("\nThe value of y = f(x) at xr = %lf is yr = %lf", xr,fy);
|
|
}
|
|
/*--------------------------- END OF PROGRAM ----------------------------*/
|