A lifetable identity. Tx is interpreted as the total years left to live above age x in the life table stationary population.
numeric. Vector of lifetable exposure.
Tx total years left to live above age x.
NA or other error checking here. This is taken as the numerator in the classic lifetable method
of calculation of life expectancy.
Preston S, Heuveline P, Guillot M (2000). Demography: measuring and modeling population processes. Wiley-Blackwell.