Spline approximation

[Fabian Grodek]

Is there any way in Excel or VBA to do a spline approximation to test data
that do not follow any polynomial shape? I mean, I have data points and I
want to approximate (i.e., not necessarily pass through the points) that data
with a spline curve.
Thanks.

Fabian

 

[Jim]

Code up in VBA the spline routines from numerical recipes. These are
actually free and available online at: http://www.nr.com/

 

[Jerry W. Lewis]

David Braden has posted code for cubic spline
http://groups.google.com/group/microsoft.public.excel.programming/msg/6a2966520eccdb1f

If you are interested, the Excel chart smoother appears to use Bezier curves
http://www.xlrotor.com/Smooth_curve_bezier_example_file.zip

Jerry

 

[Fabian Grodek]

Jim and Jerry, Thanks a lot!
From Dave Branden example I learned that "the secret" was to use an array
formula.
I coded my algorithm in VBA and it works as I wanted!
Thanks again.
Fabian