Calculate Sx, the probability of surviving into the next age group.

Description

Given a LifeTable, calculate the 'Sx', the probability of surviving into the next age group. 'Sx' is similar to the life table function 'Px', except that 'Sx' describes survival from one age group to the next, while 'Px' describes survival from one exact age to the next.

Usage

Sx(object, useLabelStart = TRUE)

## S4 method for signature 'LifeTable'
Sx(object, useLabelStart = TRUE)

Arguments

Details

'Sx' differs from other life table functions in that

• it requires all age groups (except the last) to have the same width (see hasRegularAgeTime), and

• given the same set of data, 'Sx' contains one fewer age group.

'Sx' is mainly used in models of population dynamics, such as population projections, though it occasionally appears in life tables.

If L_x is the life table population between exact ages x and x+n, then S_x = L_{x+a} / L_x, except for the second-to-last age group, where S_x = (L_{x+a} + L_x) / L_x. (S_x is not defined for the final age group.) See below for an example.

Value

An object of class Values.

See Also

To make the age groups in a life table 'regular', in the sense described in hasRegularAgeTime, use function collapseIntervals.

Examples

mx <- dembase::ValuesOne(c(0.2, 0.05, 0.1, 0.4),
               labels = c("0", "1-4", "5-9", "10+"),
               name = "age")
lt <- LifeTable(mx)
lt

## calling 'Sx' on a life table with irregular age intervals
## raises an error
## Not run: 
Sx(lt)

## End(Not run)

## collapse the intervals, and try again
lt <- collapseIntervals(lt, dimension = "age", width = 5)
lt
Sx(lt)

## use age at the end of the interval, rather than the start
Sx(lt, useLabelStart = FALSE)