gage: Gage's Extenstion to Brass' Polynomial Fertility Schedule

In gjabel/agesched: Demographic Age Schedules

Description

Provides a scaled Gage fertility schedule,

f(x) = c (x - s) (s + w - x) ^ 2

for a given set of parameter values and sequence of ages.

Usage

gage(tfr = NULL, x = seq(from = 0, to = 100, by = 1), start_fertage = 15,
  width_fertage = 35, c = 12 * w^-4 * tfr, scaled = TRUE)

Arguments

tfr	Numeric value for total fertitliy rate of the returned age schedule.
x	Vector for the sequence of ages.
start_fertage	Numeric value for the start of the fertility age range. Equivalent to s in the equation above.
width_fertage	Numeric value for the width of the fertility age range. Equivalent to w in the equation above.
c	Numeric value for a constant to control the overall fertility level. By default calcuated to approxiamate value in tfr argument.
scaled	Boolean value to return age specific fertility rates that scale to sum to tfr or not. Default TRUE.

Value

Returns the f(x) values from the Gage extenstion to Brass' schedule of age specific fertility. The age range for the calculation can take any sequence of positive numbers, such as ages in single or 5-year intervals. The function is primarily intended for use in decomposing a total fertility rate into an age-specific values.

The parameters relate to the start and width of the fertility age range (start_fertage, width_fertage) and the oveall level (tfr, c). By default s is set to 15 years and w to 33 as fixed in Brass' original schedule.

The adapted version in this function, to allow scaling to a known TFR, was based on IUSSP Demographic Models online section (see http://papp.iussp.org/sessions/papp103_s03/PAPP103_s03_040_040.html for more details).

Author(s)

Guy J. Abel

References

Gage, T. B. (2001). 'Age-specific fecundity of mammalian populations: A test of three mathematical models'. Zoo Biology 20(6):487-499.

Brass, W. (1975). Methods for Estimating Fertility and Mortality from Limited and Defective Data. Chapel Hill NC: Carolina Population Centre.

See Also

.

Examples

#single year
f0 <- gage(tfr = 1.8)
plot(f0, type = "l")

#five year
f1 <- gage(tfr = 5.8, x = seq(from = 0, to = 100, by = 5))
plot(f1, type = "l")
sum(f1) * 5

gjabel/agesched documentation built on May 17, 2019, 6:01 a.m.