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NetLogo 7 File Format

NetLogo 7 uses .nlogox files, which are XML documents (not the old plain-text .nlogo format).

Basic Structure

<?xml version="1.0" encoding="utf-8"?>
<model version="NetLogo 7.0.3" snapToGrid="false">
  <code>...</code>
  <widgets>...</widgets>
  <info><![CDATA[...]]></info>
</model>

Sections

<code>

Contains the NetLogo code (procedures, globals, etc.). XML entities must be escaped:

  • < → &lt;
  • > → &gt;
  • & → &amp;

<widgets>

Defines the Interface tab elements. Common widgets:

View (the main world display):

<view x="210" y="10" width="700" height="500"
      minPxcor="0" maxPxcor="268" minPycor="0" maxPycor="158"
      patchSize="1.0" fontSize="10" frameRate="30.0"
      wrappingAllowedX="false" wrappingAllowedY="false"
      showTickCounter="true" tickCounterLabel="ticks"
      updateMode="1"></view>
  • minPxcor/maxPxcor/minPycor/maxPycor — world dimensions in patches
  • patchSize — pixels per patch
  • wrappingAllowedX/Y — whether world wraps (toroidal)
  • updateMode — 0=continuous, 1=on ticks

Button:

<button x="20" y="20" width="80" height="40"
        display="Setup"
        forever="false"
        disableUntilTicks="false"
        kind="Observer">setup</button>
  • display — button label
  • forever — true for "forever" buttons (like go)
  • disableUntilTicks — grays out until ticks start
  • kind — "Observer", "Turtle", "Patch", or "Link"
  • Text content is the command to run

Slider:

<slider x="20" y="100" width="180" height="50"
        display="population"
        variable="population"
        min="0.0" max="1000.0" default="100.0" step="1.0"
        direction="Horizontal"></slider>
  • direction — must be capitalized: "Horizontal" or "Vertical"
  • min/max/default/step — use floats (e.g., 100.0 not 100)
  • The slider automatically creates the variable — do NOT also declare it in globals

Monitor:

<monitor x="20" y="160" width="100" height="40"
         display="Count"
         precision="0"
         fontSize="11">count turtles</monitor>

Output (text console):

<output x="20" y="200" width="180" height="150" fontSize="11"></output>

Plot:

<plot x="20" y="300" width="200" height="150"
      display="Population"
      xAxis="Time" yAxis="Count"
      xMin="0.0" xMax="100.0" yMin="0.0" yMax="100.0"
      autoPlotX="true" autoPlotY="true"
      legend="true">
  <setup></setup>
  <update></update>
  <pen interval="1.0" mode="0" display="turtles" color="-2674135" legend="true">
    <setup></setup>
    <update>plot count turtles</update>
  </pen>
</plot>

<info>

The Info tab content in Markdown format, wrapped in <![CDATA[...]]>.

Example: Minimal Model

<?xml version="1.0" encoding="utf-8"?>
<model version="NetLogo 7.0.3" snapToGrid="false">
  <code>to setup
  clear-all
  create-turtles 100 [
    setxy random-xcor random-ycor
  ]
  reset-ticks
end

to go
  ask turtles [ fd 1 rt random 30 - 15 ]
  tick
end</code>
  <widgets>
    <view x="210" y="10" width="400" height="400"
          minPxcor="-16" maxPxcor="16" minPycor="-16" maxPycor="16"
          patchSize="12.0" fontSize="10" frameRate="30.0"
          wrappingAllowedX="true" wrappingAllowedY="true"
          showTickCounter="true" tickCounterLabel="ticks"
          updateMode="1"></view>
    <button x="20" y="20" width="80" height="40"
            display="Setup" forever="false"
            disableUntilTicks="false" kind="Observer">setup</button>
    <button x="110" y="20" width="80" height="40"
            display="Go" forever="true"
            disableUntilTicks="true" kind="Observer">go</button>
  </widgets>
  <info><![CDATA[## My Model

A simple random walk model.
]]></info>
</model>

GIS Extension Notes

The GIS extension is bundled with NetLogo 7 (in extensions/.bundled/gis/).

Supported Formats

  • Rasters: ESRI ASCII Grid only (.asc or .grd). GeoTIFF is NOT supported.
  • Vectors: ESRI Shapefile (.shp), GeoJSON (.geojson)

Supported Projections

NetLogo's GIS extension only supports certain projection types. EPSG:2913 (Oregon State Plane) is NOT supported — it uses Lambert_Conformal_Conic but NetLogo wants Lambert_Conformal_Conic_2SP.

Supported projections include:

  • Transverse_Mercator (UTM zones) ← use this
  • Lambert_Conformal_Conic_2SP
  • Albers_Conic_Equal_Area
  • Mercator_1SP
  • And others (see NetLogo GIS extension docs)

For this project: Keep EPSG:2913 as the canonical CRS for analysis, but convert to UTM Zone 10N (EPSG:26910) for NetLogo.

Converting Data for NetLogo

# Reproject to UTM and convert to ASCII Grid
gdalwarp -t_srs EPSG:26910 -tr 1 1 -r bilinear input.tif output_utm.tif
gdal_translate -of AAIGrid output_utm.tif output_utm.asc

Basic Usage

extensions [gis]

globals [elevation-data]

patches-own [elevation]

to setup
  set elevation-data gis:load-dataset "/absolute/path/to/file.asc"
  gis:set-world-envelope gis:envelope-of elevation-data
  gis:apply-raster elevation-data elevation
end

Gotchas and Lessons Learned

Variables from widgets

Sliders, choosers, and switches automatically create their variables. If you also declare them in globals, you'll get "There is already a variable called X" error.

Agent references default to 0

Patch variables that store agent references (like flow-to for D8 routing) default to 0, not nobody. Use is-patch? to check validity:

; Wrong - will fail if flow-to is 0
ask patches with [flow-to != nobody] [ ... ]

; Right
ask patches with [is-patch? flow-to] [ ... ]

XML escaping in code

The <code> section is XML, so comparison operators must be escaped:

  • < → &lt;
  • > → &gt;
  • <= → &lt;=
  • >= → &gt;=

Breeds

Declare breeds before globals:

breed [waters water]

globals [ ... ]

Absolute paths

The GIS extension requires absolute paths to data files. Relative paths from the model location don't work reliably.