assessLinksFixed: Assess stability effect of a fixed link alteration

In dswdejonge/fwstability: Infer Food-Web Stability

Assess stability effect of a fixed link alteration

Description

This function assesses the effect of altering each interaction strength in a Jacobian matrix according to a fixed function on stability .

Usage

assessLinksFixed(
  JM,
  method = "eigenvalue",
  MR = NULL,
  dead_names = NULL,
  func = function(x) {
     return(x * 2)
 }
)

Arguments

JM	(required) A square named Jacobian matrix with numeric values representing the effect of one compartment (rows) on another compartment (columns).
method	(required) Either "eigenvalue" (default), "scalar", or "initial". The method "eigenvalue" finds asymptotic stability as the maximum real part of the eigenvalues calculated from the Jacobian matrix. The "scalar" method finds asymptotic stability as the scalar of natural mortality rates needed to acquire a stable matrix. The "initial" method finds initial stability as equation 4 from Arnoldi et al. (2016); initial stability is half the maximum real part of the eigenvalues derived from the matrix obtained by addition of the Jacobian matrix to its transpose.
MR	(required if method is "scalar") A named numeric vector containing mortality of the faunal compartments (per unit time, t-1). The values and names must be in the same order as the Jacobian matrix, and the values for dead compartments should be set to NA.
dead_names	(optional if method is "scalar") Character vector with all names of detritus and nutrient compartments (everything that is not fauna).
func	(required) Function describing how to alter each interaction strength to assess the effect on stability of the respective link. Default is doubling each interaction strength (interaction strength *2).

Details

If the change in stability (delta) is negative, the system becomes more stable if the respective interaction strength is altered in the Jacobian matrix (all other interaction strengths keep their original value). The system becomes less stable if delta is positive.
Using the method 'scalar' might be somewhat slower than the method 'eigenvalue'.

Value

Returns a dataframe with absolute and relative changes in stability for alteration of each interaction strength in the Jacobian matrix.

References

• de Ruiter, P.C., Neutel, A.M., Moore, J.C., 1995. Energetics, Patterns of Interaction Strengths, and Stability in Real Ecosystems. Science (80-. ). 269, 1257–1260. https://doi.org/10.1126/science.269.5228.1257

dswdejonge/fwstability documentation built on Dec. 7, 2022, 7:24 p.m.