Probability of dying in first
year of life. A numeric vector or an rvec.
sex
Biological sex. A vector the same length
as q0, with labels that can be
interpreted by reformat_sex(). Needed only when
infant is "CD" or "AK".
a0
Average age at death for infants who die.
Optional. See help for lifetab().
infant
Calculation method.
See help for lifetab().
Default is "constant".
Warning
The term "infant mortality rate" is ambiguous.
Demographers sometimes use it to refer to m0
(which is an actual rate) and sometimes use
it to refer to q0 (which is a probability.)