Doesn't give proper IRR for very negative returns

[akayvanfar]

So the gem appears to incorrectly calculate IRR (using xirr) for highly negative returns. For example, using this set of cashflows / transactions

2014-04-15 00:00:00 -0700 : -10000.0
2014-04-16 00:00:00 -0700 : -10000.0
2014-05-16 14:59:00 -0700 : 305.6
2014-06-15 23:59:59 -0700 : 9800.07
2014-06-15 23:59:59 -0700 : 5052.645

the gem gave an IRR of -107% while other tools gave an IRR of -80%. Can you guys look into this please?

Thank you.

AK

[tubedude]

@akayvanfar, out of curiosity, do you really have a cashflow that depends on the hour of the flow? I was thinking of replacing Time in favor of a Date.
Answering your question, in my branch of Finance you indeed get a IRR of -107% with the default guess. When you add a guess of -80.0 you end up with the expected result.

      @x=[]
      @x << Transaction.new(-10000.0, :date => Time.new(2014,4,15,0,0,0))
      @x << Transaction.new(-10000.0, :date => Time.new(2014,04,16,0,0,0))
      @x << Transaction.new(305.6, :date => Time.new(2014,05,16, 14,59,0))
      @x << Transaction.new(9800.07, :date => Time.new(2014,06,15, 23, 59,59))
      @x << Transaction.new(5052.645, :date => Time.new(2014,06,15, 23, 59,59))
      @x.xirr.effective.round(6) # => -1.078485
      @x.xirr(-80.0).effective.round(6) # => -0.809965

I've made a gem called XIRR that was based on finance that runs xirr calculations in two different methods. But it accepts only dates, so the result I get there is a bit different from yours:

  @x = Cashflow.new
  @x << Transaction.new(-10000.0, :date => Date.new(2014,4,15))
  @x << Transaction.new(-10000.0, :date => Date.new(2014,04,16))
  @x << Transaction.new(305.6, :date => Date.new(2014,05,16))
  @x << Transaction.new(9800.07, :date => Date.new(2014,06,15))
  @x << Transaction.new(5052.645, :date => Date.new(2014,06,15))
  @x.xirr # => -0.815121

Let me know if that is helpful.

[akayvanfar]

Thanks for the response. Weird that it is so dependent on the guess. Is there reason for that?

Using 'Date' would be fine by me. I only used 'Time' since it is what the Transaction object took. Thanks you for pointing out 'XIRR' . Our data scientist, @vnavkal , will be happy to hear that.