AKm02a0 estimates a0 using the Andreev-Kinkade rule of thumb.
AKm02a0 is an auxiliary function used by version 6 of the four HMD lifetable functions,
ltcohBoth_AxN(). This function calls
AKm02q0() to help get the work done, since the HMD needed to adapt the Andreev-Kingkade formulas to work with the period lifetable flow.
AKm02a0(m0, sex = "male")
the event / exposure infant mortality rate (not IMR)
either "male" or "female"
This is based on an MPIDR Working Paper: Andreev, Evgueni M and Kingkade, Ward W (2011) "Average age at death in infancy and infant mortality level: reconsidering the Coale-Demeny formulas at current levels of low mortality". short link: http://goo.gl/b5m5pg.
a0, the estimated average age at death of those dying in the first year of life, either a single value or a vector of a_0 values.