poplogist: Logistic Population Growth

In jarioksa/ecostudy: Ecology Teaching Package

Logistic Population Growth

Description

Function returns the expected value at a given time for the logistic population growth.

Usage

poplogist(t, r, N0, K)

Arguments

t	Time.
r	Instantaneous population growth rate.
N0	Population size at time t = 0.
K	Carrying capacity.

Details

The logistic model is usually parametrized in ecology as:

N = K/(1 + (K-N0)/N0 * exp(-r * t))

Function plogis defines a logistic model with slightly different parametrization. A similar model to poplogist can be defined as K * plogis(-log(K/N0 - 1) + r * t). Function SSlogis can be used to fit logistic model in non-linear regression (nls, lme) with yet another parametrization. SSlogis uses terms Asym, xmid and scal which can be transformed to poplogist terms as K = Asym, r = 1/scal and N0 = Asym/(exp(xmid/scal) + 1).

Value

Function returns a vector of populations sizes corresponding to input vector of t.

Author(s)

Jari Oksanen

Examples

x <- seq(0,100)
plot(x, poplogist(x, 0.1, 10, 100), xlab = "Time (t)",
  ylab="Population size (N)", type = "l")
abline(h=100, lty=2)

jarioksa/ecostudy documentation built on June 27, 2022, 6:03 a.m.