// FUNCTION TO CARRY OUT LAGRANGE INTERPOLATION

// FOR CW 1 2001/2002

// *x holds x values, *fx holds function values, ‘value’ is known x value

float Lagrange (float *x, float *fx, float value)

{

int i,j,product,sum=0.0;

// Lagrange algorithm - Eqn. 2.10

// saw code similar to this in lecture

for (i=0;i<4;i++)

{

product=fx[i]; //Correctly initialising product variable

for (j=0;j<4;j++)

{

if (i!=j) // Ensure that i=j case is not used

product=product*((value-x[j])/(x[i]-x[j])); // Calculate product

}

sum=sum+product; // Add product to running total

}

return (sum);

}