Curve fitting questions

**Joe Miller** · 12-21-2014, 08:51 AM

https://www.youtube.com/watch?v=0ienblvfddq

the link displayed above is for a utube video which teaches how to implement
built-in, sophisticated, nicely designed, user friendly excel curve fitting
features. The video is for excel 2007 and describes how to curve fit with a
power series [in addition to polynomial curve fitting, etc.]

question 1 …
does anyone know why the power series radio button choice is there, but muted, in my excel 2013?

Question 2 …
is there any good [add-in] curve fitting software out there somewhere?

Question 3 …
what is anyone’s opinion of kutools. I find mostly poor reviews on the web.

**Joe Miller** · 12-21-2014, 08:57 AM

Whoops!
Meant to submit this to the charts forum. Will try to delete and resubmit

**MrShorty** · 12-22-2014, 02:45 AM

question 1 …
does anyone know why the power series radio button choice is there, but muted, in my excel 2013?

Without seeing your data and chart, it is hard to guess. My first guess would be that you have data (such as negative or zero entries) that make no sense or otherwise cause mathematical errors in a power series.

Y=b*X^m, or, as Excel performs the regression, linearized to ln(Y)=ln(b)+m*ln(X). It should be obvious that you cannot have any negative or zero values in Y and X in order to perform this regression.

Question 2 …
is there any good [add-in] curve fitting software out there somewhere?

Unkown. I learned how to do all my regressions using Excel's built in tools: the LINEST() function for linear and linearizable equations, and Solver to perform non-linear regressions. I have no opinion or experience using other regression software (whether as an Excel add-in or as a stand alone application).