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

In FSA: Simple Fisheries Stock Assessment Methods

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

Description

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

Usage

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

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.

Value

Schnute returns a predicted size given the case of the function and the provided parameter values.

IFAR Chapter

None specifically, but 12-Individual Growth is related.

Author(s)

Derek H. Ogle, [e-mail]

References

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

See Also

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

Examples

## See the formulae
growthFunShow("Schnute",1,plot=TRUE)
growthFunShow("Schnute",2,plot=TRUE)
growthFunShow("Schnute",3,plot=TRUE)
growthFunShow("Schnute",4,plot=TRUE)

## 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")

FSA documentation built on Aug. 27, 2023, 1:06 a.m.