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Plot of the Chebyshev rational functions of order n=0,1,2,3 and 4 between x=0.01 and 100. Legendre and Chebyshev polynomials provide orthogonal families for the interval [−1, 1] while occasionally orthogonal families are required on [0, ∞). In this case it is convenient to apply the Cayley transform first, to bring the argument into [−1, 1].
The Legendre polynomials were first introduced in 1782 by Adrien-Marie Legendre [3] as the coefficients in the expansion of the Newtonian potential | ′ | = + ′ ′ = = ′ + (), where r and r′ are the lengths of the vectors x and x′ respectively and γ is the angle between those two vectors.
In statistics, ordinary least squares (OLS) is a type of linear least squares method for choosing the unknown parameters in a linear regression model (with fixed level-one [clarification needed] effects of a linear function of a set of explanatory variables) by the principle of least squares: minimizing the sum of the squares of the differences between the observed dependent variable (values ...
The independence can be easily seen from following: the estimator ^ represents coefficients of vector decomposition of ^ = ^ = = + by the basis of columns of X, as such ^ is a function of Pε. At the same time, the estimator σ ^ 2 {\displaystyle {\widehat {\sigma }}^{\,2}} is a norm of vector Mε divided by n , and thus this estimator is a ...
The orthogonality principle is most commonly used in the setting of linear estimation. [1] In this context, let x be an unknown random vector which is to be estimated based on the observation vector y. One wishes to construct a linear estimator ^ = + for some matrix H and vector c.
Orthogonal polynomials with matrices have either coefficients that are matrices or the indeterminate is a matrix. There are two popular examples: either the coefficients { a i } {\displaystyle \{a_{i}\}} are matrices or x {\displaystyle x} :
The following proof shows that the polynomials obtained from the Rodrigues' formula obey the second order differential equation just given. This proof repeatedly uses the fact that the second derivative of B(x) and the first derivative of A(x) are constants.
For example, given a = f(x) = a 0 x 0 + a 1 x 1 + ··· and b = g(x) = b 0 x 0 + b 1 x 1 + ···, the product ab is a specific value of W(x) = f(x)g(x). One may easily find points along W(x) at small values of x, and interpolation based on those points will yield the terms of W(x) and the specific product ab. As fomulated in Karatsuba ...