polynomial formula for a line graph...

[mark]

Hi.

I haven't looked at this feature in a couple of years.

Excel can give you the formula for a charted function...
what I mean is, given a few data points, it can create a
best fit curve, and display the function that it used to
do that...

Would someone remind me where, please?

Thanks.

 

[Andy Pope]

Hi,

Right click the data series and pick Add Trendline.
From the dialog you can choose the type of trend line and whether to
display the formula.

Cheers
Andy

 

[mark]

thanks.

-----Original Message-----
Hi,

Right click the data series and pick Add Trendline.
From the dialog you can choose the type of trend line

and whether to display the formula.

 

[mark]

Andy,

I followed your steps, and got a beautifully fitting 6th
order equation...

Do you know if it is possible, and if so, how, to obtain
those coefficients directly in cells, as opposed to just
on the graph?

Thanks,
Mark

 

[Andy Pope]

Hi Mark,

Have a look at Bernard's explanation.
http://www.stfx.ca/people/bliengme/ExcelTips/Polynomial.htm

Cheers
Andy

 

[mark]

Have a look at Bernard's explanation.

http://www.stfx.ca/people/bliengme/ExcelTips/Polynomial.ht

m


Hmmm.

I had looked at logest() , but not linest().

The help notes say that linest() describes a straight
line, so I hadn't looked further.

Logest() says that describes a curve, but I wasn't getting
it.

Thanks to the pointer to Bernard's explanation!

 

[Jerry W. Lewis]

Alternately, David Braden has posted VBA code to extract the
coefficients directly from the chart into cells

http://groups.google.com/[email protected]

The advantage of using the chart coefficients (either manually or via
Braden's code) is that LINEST (prior to Excel 2003) uses a numerically
inferior algorithm that can give inaccurate results with some data sets.

Jerry