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#1
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Trendline coefficients
I have fit a series of data using a 5th order polynomial from the trendline
dialog. Using the coefficients displayed in the equation, the curve is not faithfully reconstituted. Is it possible to export the trendline coefficients to arbitrary significant figures? |
#2
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Select the trendline equation on the greaph and format the number of
significant figures "MrUniverseman" wrote: I have fit a series of data using a 5th order polynomial from the trendline dialog. Using the coefficients displayed in the equation, the curve is not faithfully reconstituted. Is it possible to export the trendline coefficients to arbitrary significant figures? |
#3
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If you are absolutely, positively sure a 5th order polynomial is the
correct choice for your data fine, but you may want to check Trendline coefficients http://www.tushar-mehta.com/excel/ti...efficients.htm -- Regards, Tushar Mehta www.tushar-mehta.com Multi-disciplinary business expertise + Technology skills = Optimal solution to your business problem Recipient Microsoft MVP award 2000-2005 In article , says... I have fit a series of data using a 5th order polynomial from the trendline dialog. Using the coefficients displayed in the equation, the curve is not faithfully reconstituted. Is it possible to export the trendline coefficients to arbitrary significant figures? |
#4
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BJ has noted that you can select the graph trendline equation and
reformat it. For your purposes I recommend scientific notation with 14 decimal places. Aside from the question of potentially overfitting the data, which Tushar addresses on his web page, there is also the question of numerically fitting the model (Tushar has a heading for this, but has apparently not writen it yet). Unless your x data spans a very wide range, it is unlikely that you have adequate information to fit a 5th order polynomial. If you have Excel 2002 or earlier, and there are appreciable numeric differences between the chart trendline estimates and the LINEST estimates, then the fitting problem is ill-conditioned and the LINEST results are unreliable (the chart trendline estimates are more robust, but depending on how ill-conditioned may also be numerically unreliable). For additional discussion of this topic, see http://groups.google.com/groups?selm...0no_e-mail.com which references http://groups.google.com/groups?selm...enetserver.com Jerry MrUniverseman wrote: I have fit a series of data using a 5th order polynomial from the trendline dialog. Using the coefficients displayed in the equation, the curve is not faithfully reconstituted. Is it possible to export the trendline coefficients to arbitrary significant figures? |
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