منابع مشابه
Nearly Comonotone Approximation
We discuss the degree of approximation by polynomials of a function f that is piecewise monotone in ?1; 1]. We would like to approximate f by polynomials which are comonotone with it. We show that by relaxing the requirement for comonotonicity in small neighborhoods of the points where changes in monotonicity occur and near the endpoints, we can achieve a higher degree of approximation. We show...
متن کاملNearly Comonotone Approximation Ii
When we approximate a continuous function f which changes its monotonicity nitely many, say s times, in ?1; 1], we wish sometimes that the approximating polynomials follow these changes in monotonicity. However, it is well known that this requirement restricts very much the degree of approximation that the polynomials can achieve, namely, only the rate of ! 2 (f; 1=n) and even this not with a c...
متن کاملPositive Results and Counterexamples in Comonotone Approximation
We estimate the degree of comonotone polynomial approximation of continuous functions f , on [−1,1], that change monotonicity s ≥ 1 times in the interval, when the degree of unconstrained polynomial approximation En(f ) ≤ n−α , n ≥ 1. We ask whether the degree of comonotone approximation is necessarily ≤ c(α, s)n−α , n ≥ 1, and if not, what can be said. It turns out that for each s ≥ 1, there i...
متن کاملPositive results and counterexamples in comonotone approximation II
Let En(f) denote the degree of approximation of f ∈ C[−1, 1], by algebraic polynomials of degree < n, and assume that we know that for some α > 0 and N ≥ 2, nEn(f) ≤ 1, n ≥ N. Suppose that f changes its monotonicity s ≥ 1 times in [−1, 1]. We are interested in what may be said about its degree of approximation by polynomials of degree < n that are comonotone with f . In particular, if f changes...
متن کاملSome Positive Results and Counterexamples in Comonotone Approximation Ii
Let f be a continuous function on ?1; 1], which changes its monotonicity nitely many times in the interval, say s times. In the rst part of this paper we have discussed the validity of Jackson type estimates for the approximation of f by algebraic polynomials that are comonotone with it. We have proved the validity of a Jackson type estimate involving the Ditzian {Totik ((rst) modulus of contin...
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ژورنال
عنوان ژورنال: Journal of Approximation Theory
سال: 1998
ISSN: 0021-9045
DOI: 10.1006/jath.1998.3194