# How do i correctly interpolate between 2 positions recieved from server?

I am trying to implement interpolation in client side. I store Vector2 position data recieved from server in a list and try to interpolate (x,y) from previous position to next position as data comes. But i couldnt implement it correctly and its not smooth. Tried many differet ways, some was actually smooth by luck but i want to learn how to implement it in correct way. here i post an example code which is not smooth at all and has missing parts i guess.

Actually data comes from client1 as it moves his mouse which sends the coordinates to the server which just directs it to client2, so i dont know in which rate they are coming. I mean data is not coming in constant rate from server which is correct way to implement a server authorative game but anyway. if data must come in constant rate i can also implement it.

private final float STEP = 1.0f / 240f;
private float accumulator;
public static ArrayList<Vector2> ballPositionList = new ArrayList<>();

public void onPositionData(Vector2 positionVector){ // called when vector2 position comes from server
}

public void render(float delta) {
accumulator += delta;
while (accumulator >= STEP) {

table.act(STEP);
accumulator -= STEP;
}
table.interpolate(accumulator / STEP);
}

public void interpolate(float delta){ // tables interpolate method
if(ballPositionList.size() >1 ){
while(ballPositionList.size() > 2){ // feel like i add another boolean check here but idk what should i
ballPositionList.remove(0);

Vector2 prevPosition = ballPositionList.get(0);
Vector2 nextPosition = ballPositionList.get(1);
float interpolationFactor = delta; // this is wrong. what should it be?
float x = nextPosition.x * interpolationFactor  + prevPosition.x * (1.0f - interpolationFactor );
float y = nextPosition.y * interpolationFactor  +  prevPosition.y * (1.0f - interpolationFactor );

getBall().set(x, y);

}
}

}