Richards growth curve

Richards growth curve

Usage

richards_curve(t, y0, K, gamma, beta)

Arguments

t

Time.

y0

Cumulative count at the start of the fitting window.

K

Final epidemic size (carrying capacity).

gamma

Growth rate.

beta

Shape parameter.

Details

Parametrised so that richards_curve(0, y0, K, gamma, beta) == y0 and richards_curve(t, ...) -> K as t -> Inf, consistent with the Logistic and Gompertz curves in this package and with the standard generalised-logistic form (Richards, 1959). Note this uses exp(-beta * gamma * t) (decaying exponential); the thesis chapter this package accompanies transcribes the equation with exp(+beta * gamma * t), which drives the curve to 0 rather than to K as t grows — a sign slip relative to the standard form, corrected here (and in the revised manuscript).