Life tables are constructed from either numbers of individuals of a cohort alive at the
start of an age interval (nx) or number of individuals of a cohort dying during the age interval (dx).
Usage
lifetable(age = NULL, numbers = NULL, r = NULL, type = 1)
Arguments
age
vector of age intervals (e.g., 0 to maximum cohort age).
numbers
number of individual alive (nx) or dead (dx)
r
known rate of increase (r) for methods 3 and 4
type
numeric value of method to use to calculate life table.
1 = Age at death recorded directly and no assumption made about population stability or stability of age structure - Method 1 in Krebs (1989).
2 = Cohort size recorded directly and and no assum
Value
Dataframe containing life table values.
Details
Following Krebs (1989:413-420), standard life tables are calculated given age intervals and either cohort size or deaths.
X=age interval, nx=number of individuals of a cohort alive at the start of age interval X, lx = proportion of individuals surviving at the start of
age interval X, dx = number of individuals of a cohort dying during the age interval X,
qx=finite rate of mortality during the age interval X to X+1, px=finite rate of survival during the age interval X to X+1,
ex=mean expectation of life for individuals alive at start of age X.
For method 5, dx is corrected for population growth by dx'=dx*exp(r*x) and in method 6, nx is corrected for the same by nx*e(r*x).
See Krebs for formulae.
References
Krebs, C. J. 1989. Ecological Methodologies. Harper and Row, New York, NY. 654 p.