Model age schedules of mortality, nqx, suitable for a life table. This package
implements the SVD-Comp mortality model indexed by either child or child/adult mortality.
Given input value(s) of either 5q0 or (5q0, 45q15), the qx() function generates
single-year 1qx or 5-year 5qx conditional age-specific probabilities of dying.
See Clark (2016)