public final class Npv
Calculates the net present value of an investment by using a discount rate
and a series of future payments (negative values) and income (positive
values). Minimum 2 arguments, first arg is the rate of discount over the
length of one period others up to 254 arguments representing the payments and
args - the evaluated function arguments. Empty values are represented with
BlankEval or MissingArgEval, never null.
srcRowIndex - row index of the cell containing the formula under evaluation
srcColumnIndex - column index of the cell containing the formula under evaluation
The evaluated result, possibly an ErrorEval, never null.
Note - Excel uses the error code #NUM! instead of IEEE NaN, so when
numeric functions evaluate to Double.NaN be sure to translate the result to ErrorEval.NUM_ERROR.