Continuous factors are placed directly into the design matrix as regressors. If a column is a linear function of other columns, then the parameter for this column is marked zeroed or nonestimable. Continuous factors are centered by their mean when they are crossed with other factors (interactions and polynomial terms). Centering is suppressed if the factor has a Column Property of Mixture or Coding, or if the centered polynomials option is turned off when specifying the model. If there is a coding column property, the factor is coded before fitting.