ExcelFinancialFunctions

While the primary goal is to match Excel's behavior exactly, there are two specific areas where this library deviates to correct Excel's logic:

1. CoupDays: The library ensures that coupDays = coupDaysBS + coupDaysNC. Excel's implementation can differ by +/- one or two days when a date spans a leap year.
2. VDB (Variable Depreciation): In Excel, the depreciation in period (0,1) is not equal to the sum of depreciations in sub-periods (0,0.5) and (0.5,1). This library aims for mathematical consistency where the sum of sub-periods equals the total period depreciation.

ExcelFinancialFunctions is a .NET Standard 2.0 library. You can add it to any project that supports .NET Standard 2.0, including .NET Framework 4.6.1 or later and .NET Core 2.0 or later. Use the dotnet add package command to install it.

dotnet add package ExcelFinancialFunctions

The library provides financial functions as static methods on the Financial class within the Excel.FinancialFunctions namespace. Although the library is written in F#, it is fully compatible with C#.

using Excel.FinancialFunctions;

Console.WriteLine( Financial.IPmt(rate: 0.005, per: 53, nper: 180, pv: 200000, fv: 0, typ: PaymentDue.EndOfPeriod) );
// Displays -796.3747578439793

Console.WriteLine( Financial.Pmt(rate: 0.005, nper: 180, pv: 200000, fv: 0, typ: PaymentDue.EndOfPeriod) );
// Displays -1687.7136560969248

In F#, open the Excel.FinancialFunctions namespace to access the Financial class methods.

open Excel.FinancialFunctions

printfn "%f" <| Financial.IPmt (0.005, 53., 180., 200000., 0., PaymentDue.EndOfPeriod) 
// Displays -796.374758

printfn "%f" <| Financial.Pmt (0.005, 180., 200000., 0., PaymentDue.EndOfPeriod) 
// Displays -1687.713656