nleqslv from the findRoots(beta.init, eq.func, d.eq.func = NULL, arg.list, ...)beta should be a vector over which the zeros are sought and
the second argument arg.list a list of additional arguments.eq.func taking the same
arguments as eq.func. Supplying this function can speed up
calculations. Default is NULL.eq.func and d.eq.funcnleqslveq.func.nleqslv.findRoots calculates zeros fo the function eq.func
and is the default equation solving function in drgee.
It is supplied as a separate function in order to allow users
to use other equation solvers by writing their own wrapper
with the same interface as findRoots.nleqslv in package