@FUNCTION=OPT_BS_VEGA
@SYNTAX=OPT_BS_VEGA(spot,strike,time,rate,volatility[,cost_of_carry])
@DESCRIPTION=OPT_BS_VEGA uses the Black-Scholes model to calculate the 'vega' of a European option struck at @strike on an asset with spot price @spot.
(The vega of an option is the rate of change of its price with respect to volatility, and is the same for calls and puts.)
@volatility is the annualized volatility, in percent, of the asset for the period through to the exercise date.
@time is the time to maturity of the option expressed in years.
@rate is the risk-free interest rate to the exercise date, in percent.
@cost_of_carry is the leakage in value of the underlying asset, for common stocks, this would be the dividend yield.
* The returned value will be expressed as the rate of change of option value, per 100% volatility.
@EXAMPLES=
@SEEALSO=OPT_BS, OPT_BS_DELTA, OPT_BS_RHO, OPT_BS_THETA, OPT_BS_GAMMA
