Regression analysis

[twm145]

How can the regression analysis tool be used to find the coefficients of an
exponential equation of the form y=a + bx^m, where the coefficients a, b and
m are desired? Any help would be appreciated.

Thanks.

Tom Morris

 

[Michael R Middleton]

Tom Morris -

How can the regression analysis tool be used to find the coefficients of

an exponential equation of the form y=a + bx^m, where the coefficients a, b
and m are desired? <

I don't think there's any built-in way to fit that specific form.

The Add Trendline feature for XY charts can fit y=c*x^b (power) and
y=c*e^(b*x) (exponential). Using a log transform, the same fits can be done
using the Regression tool on the transformed data.

But you can always use Solver. Put tentative values of a, b, m (changing
cells) on the sheet; have a column of fitted y depending on those values;
summarize y and fitted y using sum of squared deviations (target cell);
minimize using Solver.

- Mike Middleton, www.usfca.edu/~middleton