portfolio object
should have two objectives: 1) mean and 2) var (or sd or StdDev). If the
portfolio object does not contain these objectives, they will be added
using default parameters.
meanvar.efficient.frontier(portfolio, R, n.portfolios = 25, risk_aversion = NULL, ...)portfolio.specn.portfolios is ignored if risk_aversion is specified and the number
of points along the efficient frontier is equal to the length of risk_aversion.optimize.portfolio