A FAMILY OF BERNSTEIN QUASI-INTERPOLANTS ON[0,1]

(整期优先)网络出版时间:1992-03-13
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SupposethatwewanttoapproximatefC[0,1]bypolynomialsinPn,usingonlyitsvaluesonXn={i/n,0≤i≤n}.ThiscanbedonebytheLagrangeinterpolantLnfortheclassicalBernsteinpolynomialBnf.But,whenntendstoinfinity,LnfdoesnotconvergetofingeneralandtheconvergenceofBnftofisveryslow.WedefineafamilyofoperatorsBkn,n≥k,whichareintermediateonesbetweenB(0)n=B1n=BnandBnn=Ln,andwestudysomeoftheirproperties.Inparticular,weproveaVoronovskaja-typetheoremwhichassertsthatBknf-f=0(n-[(k+2)/2)forfsufficientlyregular.Moreover,B(k)nfusesonlyvaluesofBnfanditsderivatiesandcanbecomputedbyDeCasteljauorsubpisionalgorithms.