growth_exp {popstudy}

Exponential growth

Description

Assuming an exponential behavior estimates the population size at time t, the growth rate, or population at time 0.

Usage

growth_exp(Nt = NULL, N0 = NULL, r = NULL, t0, t, time_interval, date = FALSE)

Arguments

Nt

numeric. The population at time t. If null and date = FALSE, then estimate the population at time t.

N0

numeric. The population at time 0. If null and date = FALSE, then estimate the population at time 0.

r

numeric. The growth rate. If null and date = FALSE, then estimate the growth rate for the time period [t0,t].

t0

numeric. An object of class character with the date for the first population.

t

numeric. An object of class character with the date for the second population.

time_interval

character. A string with the time interval to calculate Delta_t.

date

logical. If TRUE, then estimates the moment t when Nt reaches a specific value.

Value

growth_exp returns a data frame with N0, Ntr, t0, t, delta, and time_interval for desire parameters.

Author(s)

Cesar Gamboa-Sanabria

References

Shryock HS, Siegel JS (2013). The Methods and Materials of Demography, Studies in Population. Elsevier Science. ISBN 9781483289106, https://books.google.co.cr/books?id=HVW0BQAAQBAJ.

See Also

growth_linear, growth_logistic

Examples

# According to the Panama census in 2000-05-14,
# the population was 2,839,177. In 2010-05-16, the census
# calculates 3,405,813 population.
# To get r:

growth_exp(N0=2839177, Nt=3405813, t0="2000-05-14", t="2010-05-16", time_interval = "years")

# To get Nt at 2000-06-30:

growth_exp(N0=2839177, r=0.0182, t0="2000-05-14", t="2000-06-30", time_interval = "years")

# The time when the population will be 5,000,000.

growth_exp(N0=2839177, Nt=5000000, r=0.0182, t0="2000-05-14", date=TRUE)