Fix mirr function

[alexjansons]

Summary

This PR resolves 2 issues in the MIRR function implementation:

• formula calculation issue
• input parameter order

Formula Calculation Issue

The current MIRR implementation produces inaccurate results due to an error in the present value calculation.
Let's take an example from Wikipedia: Modified internal rate of return

Input data:

Cash flow values: -1000, -4000, 5000, 2000
Finance rate: 10%
Reinvestment rate: 12%

Calculation result:

• Output from current MIRR implementation: 20.57%
• Expected output based on Wikipedia example: 17.91%

The discrepancy appears due to including finance and reinvestment rates in the present value calculation. Only the finance rate should be considered.
Here is a related code fragment:

if (anIn < 0) {
   pv += anIn / Math.pow(1 + financeRate + reinvestRate, indexN++);
}

Input Parameter Order

The current implementation uses a non-standard order for finance and reinvestment rates, unlike common spreadsheet applications (Excel, Google Sheets).
Current order: (values, reinvestRate, financeRate).
Proposed order: (values, financeRate, reinvestRate).

I.e. to calculate the MIRR for the formula mentioned above one have pass the following values to Mirr#evaluate(double[] values) function:
-1000D, -4000D, 5000D, 2000D, 0.12D, 0.1D
however more the order according to most popular spreadsheet applications would be:
-1000D, -4000D, 5000D, 2000D, 0.1D, 0.12D

Testing

A test from Wikipedia has been added to verify the formula accuracy.
All other tests are left intact except for parameter order.

[pjfanning]

Thanks - merged and added the test based on https://support.microsoft.com/en-us/office/mirr-function-b020f038-7492-4fb4-93c1-35c345b53524 too

[alexjansons]

Thanks!