Today I've found interesting article here: https://habrahabr.ru/post/309210/.
After reading decided to make the same algorithm inside SMath Studio. Successfully.

ClosedCurveSpline.sm (45 KiB) downloaded 92 time(s).



Many thanks to the author of the initial article, Denxc!

Best regards, Andrey Ivashov.

Thanks Andrey for the work sheet [though it crashes 5346].
The coding is too big for my small head. Similarly to your
coding, here is attached the Mathcad "Esplina" [*.bmp].

De Boor is more a graphical closed contour based on its
convex hull properties. I was two months old in Smath
the attached de Boor was created. Maybe there is room to
compute faster.

Jean

Spline De Boor [Esplina].sm (51 KiB) downloaded 75 time(s).