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| ==Summary==
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| ==Screenshot==
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| [[Image:ConvexHull.gif]]
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| ==Download Model==
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| Download the .scn, .sel and .lse files by clicking on the following link: [[Image:ConvexHull.zip]]
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| ==Model Code Exploration==
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| In the following sections we will examine all of the model files for this model. Note that instead of downloading the zip file above, you could just copy the text in the boxes below into a text editor and save it with the appropriate name (Section title). Opening the resulting .scn file in the SELES simulator would run this model.
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| ===MLM.scn===
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| SELES Scenario
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| $gisData$ = ..\..\CaseStudy_Morice\gisData\cell
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| StudyArea = $gisData$\BEC
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| Model Dimensions: StudyArea
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| Model.sel
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| SimPriority Low Priority
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| //SimStart 100000 1
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| ===Model.sel===
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| Seles Model
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| Time Units: Step kiloStep 1000 100000
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| Landscape Events:
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| ConvexHull.lse
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| Spatial Constants:
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| StudyArea
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| Spatial Variables:
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| ConvexHullPoints[1] <= 0
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| ConvexHull[1] <= 0
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| Global Variables:
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| TRLoc = 0
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| Output Frequency: 1
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| ===ConvexHull.lse===
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| // Sweep-line approach to identifying convex hull using a worker agent
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| LSAGENT: ConvexHull
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| DEFINITIONS
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| LAYER: StudyArea, ConvexHull, ConvexHullPoints
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| GLOBAL VARIABLE: TRLoc
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| LOCAL VARIABLE: EndingPivotLoc
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| AGENT VARIABLE: PivotLocation, EdgeLocation, EdgeRow, EdgeCol
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| ENDDEF
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| INITIALSTATE
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| INITIALSTATE = 1
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| // Find the top-right-most point
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| TRLoc = 0
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| OVER REGION WHOLE MAP
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| DECISION StudyArea > 0
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| TRLoc = MAX(TRLoc, Location)
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| ENDFN
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| ConvexHull = 1 // Initialize convex hull layer to all ones (will erase areas outside hull)
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| ENDIS
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| NUMAGENTS = 1 // Only need a single worker
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| // Start on the first pivot vertex on convex hull
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| AGENTLOCATION
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| REGION LOCATION(TRLoc)
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| ENDAL
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| PROBINIT
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| PROBINIT = 1
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| // Set up first pivot vertex, and first raster boundary location
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| PivotLocation = Location
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| EdgeRow = NUMROWS-1
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| EdgeCol = COL(Location)
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| EdgeLocation = LOCATION(EdgeRow, EdgeCol)
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| EndingPivotLoc = -1
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| ENDPI
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| TRANSITIONS
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| // Continue until we reach the ending pivot location (which is actually second time we hit the second pivot vertex,
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| // since the first pivot vertex gets only partially processed on first pass)
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| TRANSITIONS = (PivotLocation NEQ EndingPivotLoc)
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| ConvexHullPoints = 1
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| // Walk line from boundary to vertex and erase until a new pivot vertex is hit (then move there)
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| oldPivot = PivotLocation
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| hitPivot = FALSE
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| OVER REGION VECTOR(EdgeLocation, PivotLocation)
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| DECISION !hitPivot
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| IF (StudyArea > 0) // hit new vertex
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| hitPivot = TRUE
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| IF (EndingPivotLoc EQ -1) AND (Location NEQ PivotLocation)
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| EndingPivotLoc = PivotLocation
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| ENDFN
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| PivotLocation = Location
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| ELSE
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| ConvexHull = 0 // erase
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| ENDFN
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| ENDFN
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| // Move boundary location clockwise around outside edge of raster
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| IF (EdgeRow EQ NUMROWS-1) AND (EdgeCol < NUMCOLS-1)
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| EdgeCol = EdgeCol + 1
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| ELSE IF (EdgeCol EQ NUMCOLS-1) AND (EdgeRow > 0)
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| EdgeRow = EdgeRow - 1
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| ELSE IF (EdgeRow EQ 0) AND (EdgeCol > 0)
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| EdgeCol = EdgeCol - 1
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| ELSE
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| EdgeRow = EdgeRow + 1
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| ENDFN
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| EdgeLocation = LOCATION(EdgeRow, EdgeCol)
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| ENDTR
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| POPULATIONTIME = 1
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| // Move to current/new pivot location
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| MOVELOCATION
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| REGION LOCATION(PivotLocation)
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| ENDML
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| ==Suggested Experiments==
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| To explore this cellular automata model further, try the following:
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