Write a user written function that expects as its input argument a vector of x values and a vector of corresponding y-values. The function must return a matrix with 3 columns. The first column must be the x-vector that was provided by the user. The other columns must contain approximations for the first derivative (dy/dx). Column 2 must contain forward difference approximations, column 3 must contain backward difference approximations. Populate the matrix with NaN if the method cannot be computed correctly for a given point.