Build a drift term

The extension point behind gddm_drift_constant() and its siblings.

Usage

gddm_drift_term(label, dpars, fn, aterms = character(0), base = FALSE)

label: One word naming the term, used when the family prints.
dpars: Named list, one entry per free parameter, each a list with link (a link name or a link object) and init, a function(y, aterms) returning a starting value on the natural scale.
fn: function(x, t, p, cov) returning the drift at each node.
aterms: Character vector of addition-term values fn reads, named as they reach the density: "vreal1".
base: TRUE if the term supplies mu and can stand alone.

A gddm_component.