Internal mpath functions
These are not intended for use by users.
findlam is to compute the maximum value of
lambda so that the coefficient estimation is zero.
g is to compute a link function (not used at this moment),
init is to compute eta, which is the estimated beta_0 in the intercept-only model.
pen_sum is to compute the total penalty value from the estimated coefficients,
llfun to compute the log-likelihood function.
convexMin (from ncvreg) calculates the lowest index for which the penalized objective function is locally convex.
Functions not used anymore: pen_eval, pen_sum, pen_zipath
Zhu Wang and author of ncvreg (see COPYRIGHTS)