Function to tabulate the values the common regressors Xc whatever the dimension.
tabulate_values(k, values, Xc0, dimXc)
a matrix of the number of times the kth value in the vector values appears.
the considered value in "values"
the different unique points of support of the common regressor Xc.
dataset containing Xc, the common regressors.
the dimension of Xc