linearnetworkanalysis

Linear Network Analysis

Here is an R/Splus language implementation of the linear network analytical methods

(they are called R/NEA*) 

originally published by Brian D. Fath and Stuart R. Borrett (2004) in MATLAB (NEA.m, version 1.0.0).

An example of usage is demonstrated: 

# parameters

#

# The input variable 'data' is an (n+1 x n+2) matrix composed of:

#

# F = flow matrix [nxn]

# z = input vector [nx1]

# x = storage vector [nx1]

# y = output vector [1xn]

# .. a 1x2 vector of zeros. 

#

# Sample data from the intertidal oyster reef ecosystem model created by Dame and Patten (1981)

# From Patten (1985).  Model flows are in kcal m^-2 day^-1;

# storage data is kcal m^-2.

# Dame, R. F., and B. C. Patten. 1981. Analysis of energy flows in an

# intertidal oyster reef. Marine Ecology Progress Series 5:115-124.

# Patten, B. C. 1985. Energy cycling, length of food chains, and direct

# versus indirect effects in ecosystems. Can. Bull. Fish. Aqu. Sci. 213:119-138.

# Network Environ Analysis

source(file.path("http://sites.google.com/site/autocatalysis/NEA.functions.r"))

# labels

Compartments = c( "Filter Feeders", "Deposited Detritus", "Microbiota",

                  "Meiofauna", "Deposit Feeders", "Predators")

# Steady-State Flow Matrix

F = matrix( c(0, 0, 0, 0, 0, 0,

              15.7915, 0, 0, 4.2403, 1.9076, 0.3262,

              0, 8.1721, 0, 0, 0, 0,

              0, 7.2745, 1.2060, 0, 0, 0,

              0, 0.6431, 1.2060, 0.6609, 0, 0,

              0.5135, 0, 0, 0, 0.1721, 0),

            nrow=length(Compartments), byrow=T, dimnames=list(Compartments,Compartments)  )

# Steady-State Storage Vector

x = c(2000, 1000, 2.4121, 24.121, 16.274, 69.237)   

# Steady-state Input Vector

z = c(41.4697, 0, 0, 0, 0, 0)

# Steady-State Outputs

y = c(25.1646, 6.1759, 5.7600, 3.5794, 0.4303, 0.3594)

# Ensure steady-state

  check.data( F,z )

# Structural Analysis

  SAnal = NEA_structure(F)

  SAnal

# Throughflow Analysis

  TFAnal = NEA_throughflow(F,y,z)

  TFAnal

# Storage Analysis

  StAnal = NEA_storage(F,x)

  StAnal

# Utility Analysis

  UtAnal = NEA_utility(F,x)

  UtAnal

# Unit Environ Analysis

  Unit.Environs = NEA_u_environs(TFAnal, StAnal)

  Unit.Environs

# Control Analysis

  CtrlAnal = NEA_control( TFAnal, StAnal )

  CtrlAnal

Source

Fath, B.D. & Borrett, S.R. 2004. A MATLAB function for Network Environ Analysis. Environmental Modelling and Software 21:375-405.