Andrych, K. D.Andronov, Ivan L.Chinarova, L. L.2017-12-212017-12-212017Odessa Astronomical publications = Одесские астрономические публикации = Одеські астрономічні публікаціїhttps://dspace.onu.edu.ua/handle/123456789/12238The methods for determination of the characteristics of the extrema are discussed with an application to irregularly spaced data, which are characteristic for photometrical observations of variable stars. We introduce new special functions, which were named as the “Wall-Supported Polynomial” (WSP) of different orders. It is a parabola (WSP), constant line (WSL) or an “asymptotic” parabola (WSAP) with “walls” corresponding to more inclined descending and ascending branches of the light curve. As the interval is split generally into 3 parts, the approximations may be classified as a “nonpolynomial splines”.envariable starseclipsing binaryminima timingsO-C analysisTYC 3692-624-1 = Gaia DR1 505352827074254080 = GSC 03692-00624Article