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# Lagrangian Interpolation

27 Mar 16, 10:39PM
Lagrangian Interpolation
I want to write a code in C++ for the Lagrangian/Polynomial interpolation for the given equation:

```void Function(p_struct particle) {

for (int X = 0; X < Nx; ++X) {
for (int Y = 0; Y < Ny; ++Y) {
Ax[X][Y] = 0;
Ay[X][Y] = 0;
}
}

for (int n = 0; n < particle.num_nodes; ++n) {
int xStart = static_cast <int> (particle.node[n].x - 3.0);
int xEnd = static_cast <int> (particle.node[n].x + 3.0);
int yStart = static_cast <int> (particle.node[n].y - 3.0);
int yEnd = static_cast <int> (particle.node[n].y + 3.0);
for (int X = xStart; X < xEnd; ++X) {
for (int Y = yStart; Y <= yEnd; ++Y) {
**// here I want to use Lagrangian Interpolation**
const double xDistance = X - particle.node[n].x;
const double yDistance = Y - particle.node[n].y;
const double delta = dirac_4(xDistance, yDistance);
Ax[X][Y] += (particle.node[n].Ax * delta);
Ay[X][Y] += (particle.node[n].Ay * delta);
}
}
}
return;
}```

How can I get interpolated values " Ax[X][Y] and Ay[X][Y]" by changing my code.

Best Regards