function lin_pred_struct_cov=define_lin_pred_struct_cov_main(cov_nodes)

%defines default structure of the linear predictor for the CPTs 
%for the case covariates but idea is same as in
%define_lin_pred_struct_cov_default

%0=main effects of covariates
%1 interaction with response categories
%2 interaction with parents 
%default = 2

lin_pred_struct_cov=zeros(1,size(cov_nodes,1));