根据已有数据以及模型（函数）预测未知区域的函数值，预测的点在已有数据范围内就是interpolation（插值），
范围外就是extrapolation（外推）。
The Difference Between Extrapolation and Interpolation
figure: The left is an example of interpolation and the right is an example of extrapolation.
转载于:https://www.cnblogs.com/tlz888/p/11434682.html
