A cubic spline of tri-monotone approximation

For any 3-monotone on $[????,????]$ function $????$ (its third divided differences are nonnegative for all choices of four distinct points, or equivalently, $????$ has a convex derivative on $(????,????)$) we construct a cubic 3-monotone (like $????$) spline $????$ with $???? \in N$ ”almost” equidis...

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Bibliographic Details
Date:2017
Author Affiliations:
  • Г. A. Дзюбенко — Мiжнародний математичний центр iм. Ю.О. Митропольського НАН України
Keywords:keywords
Main Authors: Dzyubenko, G. A., Дзюбенко, Г. A.
Format: Article
Language:Ukrainian
Published: Інститут математики НАН України 2017
Online Access:https://trim.imath.kiev.ua/index.php/trim/article/view/34
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Journal Title:Transactions of Institute of Mathematics of NAS of Ukraine
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Transactions of Institute of Mathematics of NAS of Ukraine
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Summary:For any 3-monotone on $[????,????]$ function $????$ (its third divided differences are nonnegative for all choices of four distinct points, or equivalently, $????$ has a convex derivative on $(????,????)$) we construct a cubic 3-monotone (like $????$) spline $????$ with $???? \in N$ ”almost” equidistant knots $????_????$ such that${‖???? - ????‖}_{[????_????, ????_{????-1}]} ≤ ???? ω_4 (????, (???? - ????) / ????, [????_{????+4}, ????_{????-5}] \cap [????, ????]), ???? = 1,...,????,$where $????$ is an absolute constant, $????_4 (????,????,[\cdot,\cdot])$ is the 4-th modulus of smoothness of $????$, and ${|| \cdot ||}_{[\cdot, \cdot]}$ is the max-norm.