How to find derivative values for a given 3D data.

Suppose I have data set {(x_i, y_i, z_i):i=1,2,3,4} and I want to know that derivative values. Which method is applicable here. If you have 2D data {(x_i, y_i):i=1,2,3,4} then by arithmetic mean method and geometric mean method we can find the derivative values.