Rate function throws an exception about excelfinancialfunctions

[luajalla]

Excel uses a different root-finding algo, so it's not guaranteed that the results are the same for the functions like Rate (there're other differences too).

When the approximate rates are known, it's always better to specify guess parameter. The library default guess is 0.1, which is too far from the expected value in this case and the lib doesn't find the root (we could increase the number of iterations, but that would be slower). Here that might be 0.04 or 0.05 or even 0.06.
Note, that in general case you won't get the same results as in Excel anyway

Financial.Rate(260.0,-60.0, 13500.0, 1400.0, PaymentDue.BeginningOfPeriod, 0.04)

Alternatively, you can use any solver to find the rate from FV(r,...) - fv = 0

Probably, it makes sense to adjust the algo, but hard to say what the library defaults should be.

[jcoliz]

Hi, I'm cleaning up old issues. From luajalla's comments, it seems that this issue is by design. And the behavior is covered in the docs. I don't expect any further change here, so closing.