In PredictiveEcology/NetLogoR: Build and Run Spatially Explicit Agent-Based Models

Overview

This module is a reimplementation in R using the SpaDES and NetLogoR packages of the "Wolf sheep predation" NetLogo model by Wilensky (1997, NetLogo Wolf Sheep Predation model). Please refer to the NetLogo documentation for information on the model.

Usage

library(SpaDES.core)
library(SpaDES.tools)
library(NetLogoR)

# Define the parameters
wolfSheepParams <- list(.plotInitialTime = NA, .plotInterval = NA,
                        .saveInitialTime = 0, .saveInterval = 1,
                        grassOn = TRUE, grassTGrowth = 30,
                        nSheep = 100, gainFoodSheep = 4, reproSheep = 4,
                        nWolf = 50, gainFoodWolf = 20, reproWolf = 5)

# Model init
wolfSheepSim <- simInit(
  times = list(start = 0, end = 500),
  params = list(WolfSheepPredation = wolfSheepParams),
  modules = list("WolfSheepPredation"),
  paths = list(modulePath = "./examples/Wolf-Sheep-Predation")
)

# Run the model
wolfSheepRun <- spades(wolfSheepSim)

Events

The module events recreate the model procedures from the NetLogo model which are:

the sheep move,
if grassOn = TRUE, the sheep loose energy by moving and gain energy by eating grass if there is grass to eat at their location,
the sheep with low energy die,
some sheep reproduce,
the wolves move,
the wolves loose energy by moving,
the wolves gain energy by eating a sheep if there is a sheep to eat at their location,
the eaten sheep die,
the wolves with low energy die,
some wolves reproduce,
if grassOn = TRUE, grass grow where grass has been eaten by sheep after a certain time period.

Plotting

The sheep (red) and the wolves (black) positions are plotted on the world. The world is homogeneous if grassOn = FALSE, or it is heterogeneous if grassOn = TRUE with green (1) and white (0) patches.

Saving

The size of the wolf and sheep populations are recorded in the saving event, as well as the number of green patches in the world if grassOn = TRUE.

Data dependencies

Input data

Model parameters must be defined beforehand. Otherwise, no other input data are necessary for this module.

Output data

The size of the sheep and wolf populations saved during the simulation, as well as the number of green patches if grassOn = TRUE, are available at the end of the simulation. You can access to it with wolfSheepRun$numSheep, wolfSheepRun$numWolves and wolfSheepRun$numGreen.