class CompoundInterest::Calculation

Public Class Methods

calculate(params) click to toggle source
# File lib/compound_interest/calculation.rb, line 5
def self.calculate(params)
  raise_error(params)

  @initial_payment = params[:initial_payment]
  # number of terms
  @term = params[:term]
  # interest rate per term
  @interest_rate = params[:interest_rate].to_f / 100
  # number of interest payments for the term
  @capitalization_periodicity = params[:capitalization_periodicity]
  @payment = params[:payment] || 0
  # number of payments for the term
  @payment_periodicity = params[:payment_periodicity]

  result
end
compound_interest_formula(num = 0) click to toggle source
# File lib/compound_interest/calculation.rb, line 37
def self.compound_interest_formula(num = 0)
  if num.zero?
    (1.0 + @interest_rate / @capitalization_periodicity)**(@term * @capitalization_periodicity)
  else
    (1.0 + @interest_rate / @capitalization_periodicity)**((@term * @capitalization_periodicity) -
        (@capitalization_periodicity / @payment_periodicity * num))
  end
end
periodical_payment_calculation() click to toggle source
# File lib/compound_interest/calculation.rb, line 28
def self.periodical_payment_calculation
  times = (@payment_periodicity * @term).to_i
  payment_result = 0
  (1..times).each do |i|
    payment_result += @payment * compound_interest_formula(i)
  end
  payment_result
end
raise_error(params) click to toggle source
# File lib/compound_interest/calculation.rb, line 46
def self.raise_error(params)
  raise "Argument must be Hash" if params.class != Hash
  raise ArgumentError, "Argument must include :initial_payment" if params[:initial_payment].nil?
  raise ArgumentError, "Argument must include :term" if params[:term].nil?
  raise ArgumentError, "Argument must include :interest_rate" if params[:interest_rate].nil?
  raise ArgumentError, "Argument must include :capitalization_periodicity" if [:capitalization_periodicity].nil?
end
result() click to toggle source
# File lib/compound_interest/calculation.rb, line 22
def self.result
  result = @initial_payment * compound_interest_formula
  result = periodical_payment_calculation if @payment.positive?
  result
end