# Numerical Methods: Interpolation with unequal interval with Lagrange’s method in C

**Source Code:**

///Interpolation with unequal intervals with Lagrange's Formula #include <stdio.h> #include <math.h> #include <windows.h> COORD coord = {0, 0}; void gotoxy (int x, int y) { coord.X = x; coord.Y = y; // X and Y coordinates SetConsoleCursorPosition(GetStdHandle(STD_OUTPUT_HANDLE), coord); } int main(){ float ax[20], ay[20], xp, yp = 0, dr, nr; int no_data, i, j; printf("How many data? "); scanf("%d", &no_data); printf("Enter Data: "); for(i =0; i < no_data; i++){ gotoxy(1,2+i); printf("X%d: ", i+1); scanf("%f", &ax[i]); gotoxy(10, 2+i);printf("Y%d: ", i+1); scanf("%f", &ay[i]); } printf("\nEnter value of x to find corresponding y "); scanf("%f", &xp); for(i = 0; i < no_data; i++){ dr = 1; nr = 1; for(j = 0; j<no_data; j++){ if(i!=j){ nr *= xp - ax[j]; dr *= ax[i] - ax[j]; } } yp += nr/dr*ay[i]; } printf("\nrequired value of y is: %f", yp); return 0;