Methods for calculating (usually) accurate numerical first and second
order derivatives. Accurate calculations are done using Richardson's
extrapolation or, when applicable, a complex step derivative is
available. A simple difference method is also provided. Simple
difference is (usually) less accurate but is much quicker than
Richardson's extrapolation and provides a useful cross-check.
Methods are provided for real scalar and vector valued functions.

Homepage:
https://CRAN.R-project.org/package=numDeriv
