D = VL_NUMDER(FUNC, X) computes the numerical derivative of the function FUNC at point X. X is a real array and is passed as first argument of FUNC.
D = VL_NUMDER(FUNC, X, ARG1, ARG2, ...) passes ARG1, ARG2, ... as additional arguments to the function FUNC.
See also: VL_NUMDER2(), VL_HELP().