NPV  script function
NPV() returns the aggregated net present
value of an investment based on a discount_rate per period and a series of future
payments (negative values) and incomes (positive values), represented by
the numbers in value, iterated over a number of records, as defined
by a
Syntax:
NPV(discount_rate, value)
Return data type: numeric. The result has a default number format of money.
Arguments:
Argument  Description 

discount_rate  discount_rate is the rate of discount over the length of the period. 
value  The expression or field containing the data to be measured. 
Limitations:
Text values,
Examples and results:
Add the example script to your app and run it. Then add, at least, the fields listed in the results column to a sheet in your app to see the result.
Example  Result  

Cashflow: LOAD 2013 as Year, * inline [ DateDiscountPayments 201301010.110000 201303010.13000 201310300.14200 201402010.26800 ] (delimiter is '');
Cashflow1: LOAD Year,NPV(0.2, Payments) as NPV1_2013 Resident Cashflow Group By Year; 
Year 2013 
NPV1_2013 $540.12 

Given that the LOAD Year,NPV(Discount, Payments) as NPV2_2013 Resident Cashflow Group By Year, Discount; Note that the 
