Returns the present value of an investment based on a series of periodic cash flows and a discount rate. To obtain the net present value, subtract the cost of the project (the initial cash flow at time zero) from the returned value.
返回基于一系列定期现金流和贴现率的投资现值。要获得净现值，请从返回值中减去项目成本（时间为零时的初始现金流）。