POL

POL(f;s;v) indicates that the effects of factor f are to be partitioned into polynomial contrasts (linear, quadratic etc) up to order s, where s is a scalar containing an integer between 1 and 4. Variate v defines a numerical value for each level of the factor; if omitted, the factor levels themselves are used. In a TREATMENTSTRUCTURE formula (specifying a model for analysis-of-variance), the contrasts are orthogonalized, but they are not in a regression or generalized linear model. In regression models, POL(v;s) can be used to fit simple (non-orthogonalized) polynomials of a variate v up to order s.