MIRR Function

MIRR.js

// Copyright (c) 2012 Sutoiku, Inc. (MIT License)

function MIRR(values, finance_rate, reinvest_rate) {
  // Initialize number of values
  var n = values.length;

  // Lookup payments (negative values) and incomes (positive values)
  var payments = [];
  var incomes = [];
  for (var i = 0; i < n; i++) {
    if (values[i] < 0) {
      payments.push(values[i]);
    } else {
      incomes.push(values[i]);
    }
  }
  
  // Return modified internal rate of return
  var num = -NPV(reinvest_rate, incomes) * Math.pow(1 + reinvest_rate, n - 1);
  var den = NPV(finance_rate, payments) * (1 + finance_rate);
  return Math.pow(num / den, 1 / (n - 1)) - 1;
}