# Excel 2003 to Excel 2010 LINEST formula

My formula =INDEX(LINEST(M\$21:M\$23,\$L\$21:\$L\$23^{1,1},,TRUE),1,3)

Works great in 2003 but when I run the sheet in 2010 the value's do not populate correctly. Was anything change from 2003 to 2010 in this formula?
Asked:
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Commented:
Microsoft was chastised by the academic community for errors in their statistical functions, including LINEST and LOGEST. As a result, they have revisited the code for those functions on several occasions, with the result being that you get different answers depending on which version you are using. In most cases in my experience, the differences are minor.

The most extensive rewrite occurred in Excel 2013, where a third-party firm with strong ties to academia compared the results of the revised algorithms to widely accepted statistical software packages, and found excellent agreement. In some cases, the new algorithm was noticeably slower than the original one--so the old version was retained and the new version got a different name.

Bottom line: this is a known problem. Description of the LINEST function in Excel 2003 and in later versions of Excel
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Commented:
Seems to work OK for me - I don't think anything changed in Excel 2010 that would affect LINEST - what do you mean "the values do not populate correctly" - do you get errors or the wrong results?

regards, barry
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Author Commented:
I figured something out that is very interesting. So the formula works like you said. However, I have 3 formula's like the one above.

Excel 2003 (This is what its suppose to return)

=INDEX(LINEST(M\$21:M\$23,\$L\$21:\$L\$23^{1,1},,TRUE),1,1)
Returns: 0
=INDEX(LINEST(M\$21:M\$23,\$L\$21:\$L\$23^{1,1},,TRUE),1,2)
Returns: -0.000917151
=INDEX(LINEST(M\$21:M\$23,\$L\$21:\$L\$23^{1,1},,TRUE),1,3)
Returns: 0.084003538

However, In Excel 2010

=INDEX(LINEST(M\$21:M\$23,\$L\$21:\$L\$23^{1,1},,TRUE),1,1)
Returns:  -0.000917151
=INDEX(LINEST(M\$21:M\$23,\$L\$21:\$L\$23^{1,1},,TRUE),1,2)
Returns: 0
=INDEX(LINEST(M\$21:M\$23,\$L\$21:\$L\$23^{1,1},,TRUE),1,3)
Returns: 0.084003538

As you can tell the 1 formula and 2 formula are flipped in 2010. For kicks and giggles I reversed formula 1 and 2 on 2010 and My results are correct. I don't understand how that is possible. Example of my flip are below:

=INDEX(LINEST(M\$21:M\$23,\$L\$21:\$L\$23^{1,1},,TRUE),1,2)
Returns: 0
=INDEX(LINEST(M\$21:M\$23,\$L\$21:\$L\$23^{1,1},,TRUE),1,1)
Returns: -0.000917151
=INDEX(LINEST(M\$21:M\$23,\$L\$21:\$L\$23^{1,1},,TRUE),1,3)
Returns: 0.084003538
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Commented:
OK, I see what you mean but I have no idea why these are different - I don't have Excel 2003 but it seems that there is a difference even between Excel 2007 and Excel 2010 (and the issue is with LINEST not INDEX because I took out the latter and there are differences between what LINEST returns in both versions).

I'll see if anyone else can help out........

regards, barry
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Commented:
In your desired formula, what is the purpose for listing a duplicate set of independent variables?
=INDEX(LINEST(M\$21:M\$23,\$L\$21:\$L\$23^{1,1},,TRUE),1,3)
In your formula, the ^{1,1} produces two sets of L21:L23 as values of "x" variables. But they aren't independent, so one of the two sets should be thrown out of a proper correlation. That's what Excel 2013 does--throw out the first set of L21:L23 by returning 0 for the coefficient.

To get the constant term (y-intercept), I might have used:
=INDEX(LINEST(M\$21:M\$23,\$L\$21:\$L\$23,,TRUE),1,2)
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Author Commented:
Thanks for the information. I think we will have to stay with 2003 then.
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Commented:
I think we will have to stay with 2003 then
Ooh! That's the wrong takeaway from Microsoft's KnowledgeBase article. They have finally fixed the problems with LINEST and other statistical functions in Excel 2013. Clinging to Excel 2003 will only perpetuate the possibility of error.
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Author Commented:
Thank you for the recommendation I will revisit 2013 then. We have highly statistical data that has to return consistent variable throughout many different condition so the numbers have to be correct or we cannot ship parts out the door. We have considered writing our own formula as well which might be the direction to go.
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