NetIndices (version 1.4.4.1)

PathInd: Pathway analysis

Description

Calculates the direct and indirect pathways in a network, i.e. the total system cycled throughflow, Finn's cycling index and average pathlength,...

Based on Finn(1980) (and not Finn (1976))

Usage

PathInd(Flow = NULL, Tij = t(Flow), Import = NULL, Export = NULL)

Arguments

Flow

network matrix with Flow[i,j] the flow from i (row) to j (column); component positions in rows and columns must be the same; if present, rownames or columnnames denote the compartment names.

Tij

network matrix where connectance is from column j to row i; component positions in rows and columns must be the same ; if present, rownames or columnnames denote the compartment names.

Import

vector with either the *indices* or the *names* of external compartmens from where flow enters the network; the indices point to the column positions in Tij (and the row positions in Flow).

Export

vector with either the *indices* or the *names* of external compartmens to where flow leaves the network; the indices point to the row positions in Tij (and the column positions in Flow).

Value

A list with the following items:

TSTC

total system cycled throughflow.

TSTS

non-cycled throughflow.

FCI

Finn's cycling index (1980).

FCIb

revised Finn's cycling index, sensu Allesina and Ulanowicz, 2004.

APL

average pathlength, also known as Network Aggradation (Sum of APLc and APLs in Latham 2006).

Details

The mathematical formulation of these indices can be found in the package vignette - vignette("NetIndices").

The PDF can be found in the subdirectory doc of the NetIndices package.

References

Finn JT. 1980. Flow analysis of models of the Hubbard Brook ecosystem. Ecology 61: 562-571.

Patten BC, Higashi M. 1984. Modified cycling index for ecological applications. Ecological Modelling 25: 69-83.

Patten BC, Bosserman RW, Finn JT, Cale WG. 1976. Propagation of cause in ecosystems. Patten BC, editor. Systems Analysis and Simulation in Ecology, vol. 4. Academic Press, New York. p457-579.

Allesina and Ulanowicz, 2004. Cycling in ecological netowrks: Finn's index revisited. Computational Biology and Chemistry 28, 227-233.

Kones, J.K., Soetaert, K., van Oevelen, D. and J.Owino (2009). Are network indices robust indicators of food web functioning? a Monte Carlo approach. Ecological Modelling, 220, 370-382.

Examples

# NOT RUN {
# The takapoto atoll network
PathInd(Takapoto, Import = "CO2",
        Export = c("CO2", "Sedimentation", "Grazing"))

# Conesprings is the example set 1a from Latham 2006.
as.data.frame(
  PathInd(Tij = Conesprings, Import = "Inflows",
          Export = c("Export", "Dissipation"))
)
# }