I assume those comments are addressed to me. In this forum, it is difficult to tell unless either you quote
part of the posting that you are responding to, or you write something like
@joeu2004 .
First, note that "no guess" is a
default guess of 10%, not zero.
I do not believe there is a single guess that "works" for all situations, especially for Excel XIRR.
(See my comments about XIRR unreliable in posting #18.)
And note that sometimes there are multiple IRRs for the same cash flow model. Which IRR is the "correct" one?
Some people expect a negative IRR when the sum of the cash flows is negative, and a positive IRR when the sum is positive.
But as appealing as that might seem, it is based on a fallacy.
Consider a loan of $100,000 with 12 payments of $8900. In this case, we can use Excel RATE to calculate the IRR. But I'll stick with Excel IRR to avoid confusion.
The cash flows can be either {
-100000,8900,8900,8900,8900,8900,8900,8900,8900,8900,8900,8900,8900}
or {100000,
-8900,-8900,-8900,-8900,-8900,-8900,-8900,-8900,-8900,-8900,-8900,-8900}.
Arguably, it depends on your point of view: lender or borrower. But actually, the choice of signs is arbitrary, as long as inflows and outflows have opposite signs.
SUM(
-100000,8900,8900,8900,8900,8900,8900,8900,8900,8900,8900,8900,8900) returns 6800.
SUM(100000,
-8900,-8900,-8900,-8900,-8900,-8900,-8900,-8900,-8900,-8900,-8900,-8900) returns
-6800.
So perhaps you would expect the IRRs to have opposite signs.
But in fact, both IRR({
-100000,8900,8900,8900,8900,8900,8900,8900,8900,8900,8900,8900,8900})
and IRR({100000,
-8900,-8900,-8900,-8900,-8900,-8900,-8900,-8900,-8900,-8900,-8900,-8900}) return the
same sign.
(In this case, their values differ in the last decimal place.)
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PS.... For your 3 examples, the following seems to work.
=XIRR(values, dates, IF(SUM(values)<0, -10%, 10%))
As I said, that is based on a fallacy. And it is not a panacea, since even those guesses do not work in all cases.
Perhaps you will get lucky, and that works for all of your projects.