Understanding Financial Functions in Excel

If you want to get a really good feel for these functions, you can do worse than pick up a financial RPN calculator like the HP 12C. It is largely unchanged since it was introduced in the early 80s but it’s highly functional aesthetic and purpose make for a great experience if you like to learn something new that is also genuinely useful. Personally, I keep one of these in my bag. It’s great for meetings where financials are on the table and you also don’t want the distraction of a full desktop OS around you.

Hi! Currently I am implementing those on IronCalc[1]!

They are really complex:

https://www.oasis-open.org/2021/06/16/opendocument-v1-3-oasi...

Is the odf counterpart, full on details. The libreoffice implementation:

https://github.com/LibreOffice/core/blob/9667d5e9ebe4a68a772...

I should be done within the week.

[1]: https://github.com/ironcalc/IronCalc

XIRR is laughably trivial with automatic differentiation in Haskell. Take as many iterations from the resulting [Double] as desired:

    type Cashflow = (Text, Day, Double)

    irr :: V.Vector Cashflow -> [Double]
    irr = fmap (flip findZero 0.01) npv
    
    npv :: V.Vector Cashflow -> (forall s. AD s ForwardDouble -> AD s ForwardDouble)
    npv cashflows = sum . flip discountedCashflows cashflows
      where
            discountedCashflows :: forall s. AD s ForwardDouble -> V.Vector Cashflow -> V.Vector (AD s ForwardDouble)
            discountedCashflows = fmap . presentValue

            presentValue :: forall s. AD s ForwardDouble -> Cashflow -> AD s ForwardDouble
            presentValue r (_,t,cf) = auto cf / ( (1 + r) ** numCompoundingPeriods t)

            numCompoundingPeriods t = (fromRational . toRational $ diffDays t t0) / 365.0

            t0 = maybe (toEnum 0) viewInvestmentDate $ cashflows V.!? 0

            viewInvestmentDate = view _2