Search results
Results from the WOW.Com Content Network
In mathematics, least squares function approximation applies the principle of least squares to function approximation, by means of a weighted sum of other functions.The best approximation can be defined as that which minimizes the difference between the original function and the approximation; for a least-squares approach the quality of the approximation is measured in terms of the squared ...
It was first proved by Hassler Whitney in 1957, [1] and is an important tool in the field of approximation theory for obtaining upper estimates on the errors of best approximation. Statement of the theorem
What is meant by best and simpler will depend on the application. A closely related topic is the approximation of functions by generalized Fourier series, that is, approximations based upon summation of a series of terms based upon orthogonal polynomials.
The polynomial of best approximation within a given subspace is defined to be the one that minimizes the maximum absolute difference between the polynomial and the function. In this case, the form of the solution is precised by the equioscillation theorem .
The conventional Padé approximation is determined to reproduce the Maclaurin expansion up to a given order. Therefore, the approximation at the value apart from the expansion point may be poor. This is avoided by the 2-point Padé approximation, which is a type of multipoint summation method. [9]
For example, given a function defined on the interval [,] and a degree bound , a minimax polynomial approximation algorithm will find a polynomial of degree at most to minimize max a ≤ x ≤ b | f ( x ) − p ( x ) | . {\displaystyle \max _{a\leq x\leq b}|f(x)-p(x)|.} [ 3 ]
In approximation theory, Jackson's inequality is an inequality bounding the value of function's best approximation by algebraic or trigonometric polynomials in terms of the modulus of continuity or modulus of smoothness of the function or of its derivatives. [1]
In other words, if the same rational function appears more than once in the table, that rational function occupies a square block of cells within the table. This result is known as the block theorem. If a particular rational function occurs exactly once in the Padé table, it is called a normal approximant to f(z). If every entry in the ...