Class: Valuation::InterestRate

Inherits:
Object
  • Object
show all
Defined in:
lib/valuation/interest_rate.rb

Constant Summary collapse

@@periods = 
{:yearly => 1.0,
:semiannually => (1/2.0),
:bi_annually => (1/2.0),
:quarterly => (1/4.0),
:monthly => (1/12.0),
:weekly => (1/52.0),
:daily => (1/365.0)}

Instance Attribute Summary collapse

Class Method Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(rate, type = :yearly, options = {}) ⇒ InterestRate

All interest rates are converted to EAR rates.

So the base time period is one year. 

10% EAR rate: InterestRate.new(0.10)

5% EMR rate: InterestRate.new(0.05, :monthly)

12% APR compounded monthly InterestRate.new(0.12, :apr, :compounded => :monthly)

Custom Period 5% Compounded every third of the year InterestRate.new(0.05, 1/3.0)



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# File 'lib/valuation/interest_rate.rb', line 49

def initialize(rate, type=:yearly, options = {})
  if type.class.to_s == 'Float'
    @rate = convert_period(1/type, rate)
  elsif type.to_sym == :apr
    options = {:compounded => :yearly}.merge(options)
    factor = @@periods[options[:compounded]]
    @rate = (1 + (rate*factor.to_f))**(1/factor.to_f) - 1
  else
    @rate = convert_period(1/@@periods[type], rate)
  end
end

Instance Attribute Details

#rate ⇒ Object

Returns the value of attribute rate.



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# File 'lib/valuation/interest_rate.rb', line 5

def rate
  @rate
end

Class Method Details

.add_time_periods(periods) ⇒ Object

Add a unique time period. If you need different time periods that are not provided by default

All time periods are measured to a base time period of 1 year so to add an hourly time period

InterestRate.add_time_periods(:hourly => (1/(365*24))) This time period will now be available, in the init method. It will also add a instance method hourly



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# File 'lib/valuation/interest_rate.rb', line 30

def self.add_time_periods(periods)
  @@periods.merge(periods)
  periods.each_pair do |period, n| 
    define_method "#{period}" do
      convert_period n
    end
  end
end

Instance Method Details

#continuous(t) ⇒ Object

The continous interest rate for a given time period t



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# File 'lib/valuation/interest_rate.rb', line 62

def continuous(t)
  E ** (rate * t) - 1
end