Accessing values in exponential trendline equation

[jstansbury]

Hi,
I need to access the calculated values in the equation for an expontial
trendline. I'd rather not have to create a chart and trendline and then
manually enter the values. I know how to get the slope and intercept via
functions, but need the "a" and "b" values from y = ae^bx. Any tips or help
very much appreciated.
Thanks,
j

 

[Jerry W. Lewis]

y = a*e^(b*x)
is equivalent to
ln(y) = ln(a) + b*x
You can then use SLOPE() and INTERCEPT() to get b and ln(a). This is
equivalent to what is done when you fit the chart exponential trendline.

Jerry

 

[Guest]

Is there a similar way to work a mulitple order polynomial trendline equation?

 

[Jon Peltier]

Bernard Liengme has an example worked out for you:

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

- Jon
-------
Jon Peltier, Microsoft Excel MVP
Peltier Technical Services
Tutorials and Custom Solutions
http://PeltierTech.com/
_______

 

[Jerry W. Lewis]

LINEST in some cases can be subject to numerical difficulties. The
safest course is to request a chart polynomial trendline and verify that
the coefficients are consistent with those given by LINEST.
Interestingly, the chart polynomial trendline (formatted to display full
precision) is better than almost all dedicated statistics packages.
Alternately, David Braden has posted VBA code to extract the
coefficients directly from the chart into cells

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

Jerry