xnfx - High order predictor matrix for regression analysis

extension of x2fx to generate higher order predictor matrix for regression analysis

An extension to X2FX which can convert predictors to design matrix to higher order (equal or lower than dimension of x).

Let A and B represent the two columns of X. The rows of the MODEL matrix specify the terms 1, A, B, C, A.*B, A.*C, B.*C, A.^2, B.^2, C.^2, A*B*C, A.^3, B.^3, C.^3.