I also have trouble with the formula from adding a trendline to a 4th order polynomial. I graphed data in both 2003 and 2007 and added a 4th order trendline and displayed the formula on the graph. In both versions, I got the same formula, specifically, y = 0.00000095x4 - 0.00753977x3 + 22.51174905x2 - 29,872.75x + 14,865,177. This yielded 46690 for my text x value of 1980, but I expected a number less than 1.

The formula using linest was: y = -3.3105E-10x^4+1.77394E-06x^3+-0.002673x^2+0x+1798.06, which yields the expected 0.0065 for the x value of 1980.

Quite a bug!

Note: I also tried a 2nd order polynomial. The results were the same using linest and using the formula on the chart from the treadline. No bugs.

Martin Brown wrote:

Re: Excel 2007 Polynomial Order Incorrect

14-Dec-07

If you run the same dataset under 2003 do you get the roughly the same

coefficients for a 4th order fit as are displayed in 2007 but with one

value hidden. Or is 2007 actually doing a 3rd order fit wh

Previous Posts In This Thread:

Excel 2007 Polynomial Order Incorrect

We recently upgraded to Office 2007. When we attempt to do a trendline in

Excel, the order of polynomials is always one below what it is stated to be

and the highest ordered polynomial is always wrong

Have your downloaded Office 2007 SP1 and tried trendlines again?

Have your downloaded Office 2007 SP1 and tried trendlines again?

Download info:

http://support.microsoft.com/kb/936982
I was unable to get to your file - my email address was rejected

best wishes

--

Re: Excel 2007 Polynomial Order Incorrect

SP1 did not fix the problem.

:

Re: Excel 2007 Polynomial Order Incorrect

Martin,

Here is a link to the file:

http://www.mediafire.com/?7g4abmw30wn
In 2003 we were getting the correct values. 2007 is doing a 3rd order fit

when we click 4th order (and the 3rd order is wron

Re: Excel 2007 Polynomial Order Incorrect

If you run the same dataset under 2003 do you get the roughly the same

coefficients for a 4th order fit as are displayed in 2007 but with one

value hidden. Or is 2007 actually doing a 3rd order fit wh

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