Excel Function to Match Power Trendline in Chart?

[acjim]

Hi,

I'm using the "Power" trendline in an XY scatter chart and want to use
the formula and the rsquared result in a worksheet.

What worksheet function can I use to to show the function (or it's
components) and the rsquared within the worksheet?

(The formula stated on the chart is: y = 644.691x^-0.895)

I've looked at LINEST but that seems to only give a straight line
trend?

LOGEST gives me the exponential result?

Basically I'm worried about using the rsquared value from the chart if
I don't have it through a function as well.

Anyone able to help?

Thanks!

 

[Jerry W. Lewis]

Despite extremely misleading text in Help, LINEST is not limited to
straight lines; it fits models that are linear in the unknown
coefficients (polynomials, etc.), cf.
http://www.stfx.ca/people/bliengme/ExcelTips/Polynomial.htm
If y=a*x^b then ln(y)=ln(a)+b*ln(x), which the chart trendline uses to
estimate the coefficients. In that second form, you can use LINEST, or
SLOPE, INTERCEPT, and RSQ. If you do not have Excel 2003,
http://groups-beta.google.com/group...orksheet.functions/msg/d6a03470e7a1c650?hl=en
suggests alternate calculations that will be more accurate in certain
circumstances.

Jerry