code: public static double toAnnualReturnFromGrowthFactor(double growthFactor, CalendarDateUnit growthFactorUnit) {
          double tmpGrowthFactorUnitsPerYear = growthFactorUnit.convert(CalendarDateUnit.YEAR);
          return PrimitiveMath.POW.invoke(growthFactor, tmpGrowthFactorUnitsPerYear) - PrimitiveMath.ONE;
      }
docs: GrowthRate = ln(GrowthFactor)
  
  @param growthFactor A growth factor per unit (day, week, month, year...)
  @param growthFactorUnit A growth factor unit
  @return Annualised return (percentage per year)