Orthonormal Polynomial Approximation of Mineral Water Data with Errors in Both Variables

In this paper we introduce the data from mineral water probe with errors in both variables. For this case we apply our orthonormal polynomial expansion(OPEM) method to describe the data in the new error corridor. It receives the approximating curves and their derivatives including the errors by weighting approach. The numerical method and approximation results are presented and discussed. The special criteria are carried out for orthonormal and evaluated from it usual expansion. The numerical results are shown in tables and figures.