smoothing lines

[Anne]

In the scatter plot option, lines can be smoothed. what
is the formula used for the smoothing, what is the
smoothing technique called, and is there any documentation
of the calculations used in Excel for smoothing the lines?
thanks.

 

[J.E. McGimpsey]

AFAIK, the method is unpublished. I've seen various assertions that
the method uses cubic splines, though with some tweaks.

There are dozens of threads on this in the archive:

http://google.com/advanced_group_search?q=group:*excel*

Use "smooth chart" (no quotes) as a search term. Look for posts by
David Braden, Jerry W. Lewis and Jon Peltier, among others.

 

[Jerry W. Lewis]

Excel's chart smoother appears to use Bezier curves. Brian Murphy has
posted code for Bezier curves.

http://www.xlrotor.com/excel_stuff.htm

In most cases, the difference between Bezier curves and cubic splines is
minimal. An example where the difference is noticeable is

http://www.google.com/groups?threadm=3E7291CA.7020907@no_e-mail.com

David Braden has posted code for cubic splines

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

Jerry