This PR resolves all known bugs and adds new Excel functions introduced since the library was originally created.
Add PDURATION function. Returns the number of periods required by an investment to reach a specified value. (Resolves #62)
Add RRI function. Also used for CAGR. Returns an equivalent interest rate for the growth of an investment. (Resolves #60)
Improve XIRR function by reducing the precision required before an answer is returned. (Fixes #27)
Improve ACCRINT function by allowing first interest date on the settlement date. (Fixes #22)
Add PriceAllowNegativeYield function, which operates like the PRICE function except that it allows negative yield inputs. This is experimental. We'd love feedback on how this works for folks. (Fixes #13)
This PR resolves all known bugs and adds new Excel functions introduced since the library was originally created.