property A: TMtx;
Independent variables.
Result: stored in self (calling object), returns self for chaining
Remarks:
Defines logistic regression matrix of independent variables. Suppose y takes values in k ordered categories, and let p_ij be the cumulative probability that y(i) falls in the j'th category or higher. Ordinal logistic regression model is defined as:
logit(p_ij) = theta(j) + A_i'B , i = 1,..,length(Y), j = 1,..,k-1, where A_i is the i'th row of A . The number of ordinal categories k is taken to be the number of distinct values of int(y). If k is 2 the model is ordinary logistic regression.