This function wraps the two approximations for a0 based on either q0 (IMR) or m0.

lt_rule_1a0_ak(M0 = NULL, q0 = NULL, Sex)

## Arguments

M0 a value or vector of values of 1m0, the death risk in the first year of life. a value or vector of values of 1q0, the death probability in the first year of life, sometimes approximated with IMR. either "m" or "f"

## Value

a0, the estimated average age at death of those dying in the first year of life, either a single value or a vector of values.