根据函数在一些离散点的函数值，推算它在某点的导数或某高阶导数的近似值。通常用差商代替微商，或用一能近似代替该函数的较简单的函数（如多项式、样条函数）的相应导数作为所求导数的近似值。(According to the function value of some discrete points in the function, the derivative of the derivative at a given point or the approximation of a higher order derivative is calculated. Usually with difference quotient instead of derivative, or one can approximate the function instead of a simple function (such as polynomial, spline function approximation) the corresponding derivative as the derivative value.)