Posted by
Nathaniel Ryckman on
May 19, 2011; 6:52pm
URL: http://imagej.273.s1.nabble.com/Power-Curve-fitting-SLope-and-intercept-different-than-Excel-tp3684501p3684507.html
Here is a little tip.
If you go to a doctor and the doctor makes a diagnosis that is severe, might you not seek a second opinion just in case? This is an easy way you can test the reliability of computer software that you use.
Also, the general rule of thumb is that software that is more widely used is going to have gone through more testing than obscure software.
So, in this case, here are a couple things you can do:
1) Compare excel with TI-89 (if it's just curve fitting) or use Mathematica/Matlab/Maple
2) Google "imagej CurveFitter error" and "excel trendline error"
In this case, I would guess that the rule of thumb is wrong because of this discussion I found by Googling:
http://www.pcreview.co.uk/forums/error-trendline-equation-3rd-order-and-higher-polynomials-t3830270.html"As I recall, there are some issues with graph trendlines in 2007, but another
common problem is failure to display enough figures to have any chance of
calculating effectively with them. I'm not sure about 2007, but in previous
versions, you could right click on the equation and format to display in
scientific notation with 14 decimal places.
Also note that you can fit polynomials with LINEST. For example, to fit a
cubic with intercept forced to be 0, you would select 3 adjacent cells and
array enter the formula
=LINEST(y,x^{1,2,3},FALSE)
Jerry"