FSA (version 0.8.6)

Schnute: The four-parameter growth function from Schnute (1981).

Description

The four-parameter growth function from Schnute (1981). Use SchnuteModels() to see the equations for each growth function.

Usage

Schnute(t, case = 1, t1 = NULL, t3 = NULL, L1 = NULL, L3 = NULL,
  a = NULL, b = NULL)

SchnuteModels(cex = 1.25, ...)

Arguments

t

A numeric vector of ages over which to model growth.

case

A string that indicates the case of the Schnute growth function to use.

t1

The (young) age that corresponds to L1. Set to minimum value in t by default.

t3

The (old) age that corresponds to L3. Set to maximum value in t by default.

L1

The mean size/length at t1.

L3

The mean size/length at t3.

a

A dimensionless parameter that is related to the time/age at the inflection point.

b

A dimensionless parameter that is related to size/length at the inflection point.

cex

A single numeric expansion value for use with SchnuteModels.

...

Not implemented.

Value

• Schnute returns a predicted size given the case of the function and the provided parameter values. SchnuteModels returns a graphic that uses plotmath to show the growth function equation in a pretty format.

IFAR Chapter

None specifically, but 12-Individual Growth is related.

References

Schnute, J. 1981. A versatile growth model with statistical stable parameters. Canadian Journal of Fisheris and Aquatic Sciences 38:1128-1140.

See Also

See vbFuns, GompertzFuns, RichardsFuns, and logisticFuns for similar functionality for other models.

Examples

## See the formulae
windows(5,5)
SchnuteModels()

## Simple examples
ages <- 1:15
s1 <- Schnute(ages,case=1,t1=1,t3=15,L1=30,L3=400,a=0.3,b=1)
s2 <- Schnute(ages,case=2,t1=1,t3=15,L1=30,L3=400,a=0.3,b=1)
s3 <- Schnute(ages,case=3,t1=1,t3=15,L1=30,L3=400,a=0.3,b=1)
s4 <- Schnute(ages,case=4,t1=1,t3=15,L1=30,L3=400,a=0.3,b=1)

plot(s1~ages,type="l",lwd=2)
lines(s2~ages,lwd=2,col="red")
lines(s3~ages,lwd=2,col="blue")
lines(s4~ages,lwd=2,col="green")