genVal method
Generates a new dot based on the previous dot. Increments x by 1 and computes: y = 10 * sin(x/4) + Random(0, 5)
Implementation
Offset genVal(Offset previous) {
final newX = previous.dx + 1;
final newY = 10 * sin(newX / 4) + random.nextDouble() * 5;
return Offset(newX, newY);
}