nlraa (version 0.53)

SSbgf: self start for Beta Growth Function

Description

Self starter for Beta Growth function with parameters w.max, t.m and t.e

Usage

bgf(time, w.max, t.e, t.m)
SSbgf(time, w.max, t.e, t.m)
bgf2(time, w.max, w.b, t.e, t.m, t.b)

Arguments

time

input vector (x) which is normally ‘time’, the smallest value should be close to zero.

w.max

value of weight or mass at its peak

t.e

time at which the weight or mass reaches its peak.

t.m

time at which half of the maximum weight or mass has been reached.

w.b

weight or biomass at initial time

t.b

initial time offset

Value

bgf: vector of the same length as x (time) using the beta growth function

bgf2: a numeric vector of the same length as x (time) containing parameter estimates for equation specified

Details

For details see the publication by Yin et al. (2003) “A Flexible Sigmoid Function of Determinate Growth”.

The form of the equation is: $$w.max * (1 + (t.e - time)/(t.e - t.m)) * (time/t.e)^(t.e / (t.e - t.m))$$. Given this function weight is expected to decay and reach zero again at \(2*t.e - t.m\).

Examples

# NOT RUN {
## See extended example in vignette 'nlraa-AgronJ-paper'
x <- seq(0, 17, by = 0.25)
y <- bgf(x, 5, 15, 7)
plot(x, y)
# }

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