Re: [office-formula] IRR Office-1054

[Eike Rathke <erack@sun.com>]

Hi Patrick,

On Tuesday, 2010-03-30 17:17:06 -0400, Patrick Durusau wrote:

> Note that the syntax include the default 0.1 value.
>
> Rob has proposed:
>
>> Semantics: Compute the internal rate of return for a series of cash  
>> flows.
>>
>> The result of IRR is the rate at which the NPV() function will return  
>> zero with the given Values.
>>
>> There is no closed form for IRR. Implementations typically return an  
>> approximate solution using an iterative method, in which case the  
>> Guess parameter may be used to initialize the iteration. If the  
>> implementation is unable to converge on a solution given a particular  
>> Guess, it may return an error. 
>
> OK, no problem with first two sentences.
>
> What to do with the default value in the syntax if we drop it from  
> semantics?

Keep it.

> Further suggestion, why not simply say:
>
> "If provided, Guess is an estimate of the interest rate to start the  
> iterative computation. If omitted, the value 0.1 (10%) is assumed. If an  
> evaluator is unable to converge on a solution given a particular Guess,  
> it may return an error."

Looks good to me.

  Eike

-- 
Automatic string conversions considered dangerous. They are the GOTO statements
of spreadsheets.  --Robert Weir on the OpenDocument formula subcommittee's list.

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