Orthogonal models of structure functions

Approximation of structure functions (SFs) using orthogonal polynomials in most cases, leads to an incorrect determination of the spectral power density for the obtained orthogonal model. A method for constructing orthogonal models of SFs is proposed based on preliminary shifting of the analyzed SF and using orthogonal functions as the bases. In this method, the expansion coefficients are determined using a numerical-analytical approach, which allows one to determine orthogonal models of SFs with a small approximation error and calculate spectral power density with greater accuracy. The implementation of the algorithms for constructing orthogonal models of SFs in the Laguerre and Legendre bases is considered.