Requred Number of Nodes in Akima

MichaelScheffenacker · **Joined:** Wed May 22, 2013 3:09 pm **Posts:** 1

Regarding to your manual (VB6) 5 nodes are required for a Akima spline interpolant; regarding to literature 4 should be sufficient. Is it possible to run the alglib Akima with just 4 nodes?

Code:

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'This subroutine builds Akima spline interpolant

INPUT PARAMETERS:
    X           -   spline nodes, array[0..N-1]
    Y           -   function values, array[0..N-1]
    N           -   points count, N>=5

Sergey.Bochkanov · **Joined:** Fri May 07, 2010 7:06 am **Posts:** 927

I've studied algorithm one more time, and - yes, it is possible. Akima spline with N=4 will become parabolic spline (or something like this), and everything should work. BTW, newer versions of ALGLIB will throw exception for N=4 so you will have to comment out line which performs check for N being >=5.

Sergey.Bochkanov · **Joined:** Fri May 07, 2010 7:06 am **Posts:** 927

BTW, I've added support for N=2...4 to issues tracker, so it will appear in 3.8.0

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