Extract interpolation data from chart?

  • Thread starter Thread starter James
  • Start date Start date
J

James

I am sure this has been asked before, but have had a look round &
couldnt find anything.

I have a worksheet with 4 speed values in mph, & then a second column
stating time.
e.g.
Speed Time
30 3.5
60 7.2
90 12.9


I can chart this as an x/y plot & create a smoothed line which shows
the acceleration curve of speed/time.

What I would like to do is get access to the interpolated values &
being to construct a distance/time graph based on this.

Is it possible?

Cheers,

James
 
A linear fit is fairly close to the observed points, and can be obtained
by LINEST() or by SLOPE() and INTERCEPT().

A quadratic fit exactly passes through all three points, and can be
obtained by LINEST().

The smoothed chart connecting line is not as strongly curved as the
quadratic fit. 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
 
Back
Top