andersen: Andersen Selectivity Function

In IMPRESSPROJECT/ModelingPopulation: Modeling of an exploited population (structured by age)

Description

Computes Andersen selectivity function.

Usage

andersen(x, p1, p3, p4, p5)

Arguments

x	Points where Andersen function (see Details) must be computed.
p1	Define the value of x at which the transition between the two gaussian functions happens; that is, x=p5/exp(p1). Negative values are NOT valid.
p3	Ascending slope parameter. Negative values or zero are NOT valid.
p4	Descending slope parameter. Negative values or zero are NOT valid.
p5	Define the value of x at which the transition between the two gaussian functions happens; that is, x=p5/exp(p1). Negative values or zero are NOT valid.

Details

The function implements Andersen selectivity function whose equation is

S(x)<-p0+p2exp(-(ln(p5/x)-p1)^2/p4) if ln(p5/x)<=p1

and

S(x)<-p0+p2exp(-(ln(p5/x)-p1)^2/p3) if ln(p5/x)>p1.

We fixed p0=0, which is the beginning size for the plateau, and p2=1, which is the maximum value attainable by the function. Remember that p3 and p4 are the ascending and descending slope parameters, respectively, whereas p1 and p5 define the value of x at which the transition between the two gaussian functions happens; that is, x=p5/exp(p1).

Value

SA: Vector containing the values of Andersen function in each of the x-values.

Author(s)

• Marta Cousido-Rocha

• Santiago Cerviño López

IMPRESSPROJECT/ModelingPopulation documentation built on March 21, 2020, 12:14 a.m.