Turtles Behaviour - On the Move

Neighbors

In NetLogo, the neighbors primitive is used to identify the patches that surround a given patch. Specifically, it reports an agentset containing the eight patches that are adjacent to the caller patch. These include the patches to the north, south, east, west, and the four diagonals: northeast, northwest, southeast, and southwest.

Here’s a basic overview of how the neighbors primitive works:

  • Usage: neighbors is typically used in the context of a patch, which means it must be called by a patch or within a ask patches context.

  • Example:

  • Behavior: When a patch calls neighbors, it collects and returns an agentset of the eight surrounding patches. If the world wraps (set by set-patch-wrap?), the edges will seamlessly connect, so every patch still has eight neighbors even at the boundaries.

  • Application: This primitive is often used in models that simulate interactions across a grid, such as cellular automata, diffusion models, or any scenario where local neighborhood interactions are important.

Keep in mind that if a patch is on the edge and the world does not wrap, it will still return neighbors, but those outside the grid’s boundary will not be included in the agentset.

patch-ahead

patch-ahead

The patch-ahead primitive in NetLogo is used to reference a patch that is located a certain distance ahead of the current agent (most often a turtle). The syntax is:

  • distance: A number specifying how far ahead in the turtle’s current direction you want to look. If you specify a positive number, it will look forward in the direction the turtle is facing. A negative number would look behind the turtle.

Example Usage:

In this example, each turtle checks the color of the patch one step directly in front of it. If the patch’s color is black, the turtle moves forward by one step (fd 1).

patch-left and patch-right

These primitives let you reference a patch to the left or right of a turtle at a specified angle and distance. They allow for checking patches that are not directly in front.

  • patch-left: Returns the patch a certain distance away at a specified angle to the left of the current heading.

    Syntax:

  • patch-right: Returns the patch a certain distance away at a specified angle to the right of the current heading.

    Syntax:

Example Usage:

These would return patches located one step away at a 45-degree angle to the left and right of the turtle’s current heading.

patch-at

patch-at is another useful primitive that allows you to reference a patch located at a specific offset in terms of coordinates from the current location of the turtle.

Syntax:

  • dx: The change in x-coordinate.
  • dy: The change in y-coordinate.

Example Usage:

This would reference the patch one unit to the right and one unit up from the turtle’s current position.

patches-at

patches-at returns an agentset of patches located at specified relative coordinates (offsets) from the calling agent’s position.

Syntax:

  • The offsets are provided in pairs, representing x and y changes.

Example Usage:

This would affect the patches directly adjacent to the turtle (north, south, east, and west) by setting their color to red.

patches in-radius

This primitive returns an agentset of patches within a specified radius of the calling agent.

Syntax:

Example Usage:

Each of these commands provides ways to navigate and interact with the spatial environment in NetLogo, crucial for models that rely on spatial relationships and movements.

Move-To

In NetLogo, the primitives move-to and one-of are used to control agent movement and to select a random agent from an agentset, respectively. Let’s break down each primitive and examine how they can be combined.

move-to

  • Purpose: The move-to primitive is used to move a turtle to a specific location, which can be either a patch or another turtle.

  • Usage:

  • Behavior: When a turtle uses the move-to command, it changes its coordinates to the location of the target patch or turtle. If moving to another turtle, both turtles end up on the same patch.

Move-to green patches

The main issue in the code is with the logic in the move procedure, where you’re trying to make turtles move to green patches within a specified radius. Here are some key problems with the current implementation:

  1. Using if close-patch = green: The variable close-patch is a patch set, not a single patch or color. You need to check if any of those patches are green.

  2. Logic for moving turtles: The turtles need to select a particular patch with a specific color (green in this case) and then move to it. The current logic doesn’t correctly find and move to a green patch.

  3. Use of ask: The way you’ve structured the code may misunderstand NetLogo’s command context, especially if you’re new to the language’s scoping rules.

Here’s a corrected version of your code:

Explanation:

  1. let close-patches patches in-radius 5: This finds all the patches within a radius of 5 around each turtle.

one-of

  • Purpose: The one-of primitive selects a single random agent from an agentset.

  • Usage:

  • Behavior: one-of returns one agent from the provided agentset at random. If the agentset is empty, it returns nobody.

Combining move-to and one-of

You can use move-to with one-of to make a turtle move to a random location or towards a random agent. Here is an example:

  • Explanation: In these combined usages, one-of first selects a random patch or turtle, and then move-to moves the calling turtle to the location of that selected patch or turtle. This combination is useful for behaviors where randomness or diffusion-like movements are modeled.

Move and max-to

turtles-own [energy]
patches-own [fertility]

to setup
  clear-all
  create-turtles 10 [
    setxy random-xcor random-ycor
    set energy random 10
  ]
  ask patches [
    set fertility random 10
    set pcolor scale-color green fertility 0 10
  ]
  reset-ticks
end

to go
  ask turtles
  [
    move
  ]
end


to move
  let close-patch patches in-radius 1
  if any? close-patch [
    let most-fertile-patch max-one-of close-patch [fertility]
    move-to most-fertile-patch
  ]
end

In NetLogo, the max primitive indeed returns the maximum value from a set of numbers, but it does not provide information about which agent possesses that value. This is why max-one-of or with-max is often used in such scenarios, as they directly return the agent with the maximum value of a specified attribute.

However, if you really want to use max and manipulate it to still identify the corresponding patch, you would have to perform additional steps to match the maximum value back to the agent. Here’s how you can do it:

to move
  let close-patch patches in-radius 1
  if any? close-patch [
    let max-fertility max [fertility] of close-patch
    let most-fertile-patch one-of close-patch with [fertility = max-fertility]
    move-to most-fertile-patch
  ]
end

Target

In NetLogo, there isn’t a built-in command called target. Instead, you might have seen that it’s common to use the word target as a variable name to represent a specific agent (such as a patch or turtle) that another agent might move towards or interact with. This is a concept utilized in agent-based modeling to manage dynamic interactions.

Here’s how you might typically see target used in NetLogo code:

Using target as a Variable

  1. Selecting a Target: In this context, target is a variable name created by the user to represent a particular patch or turtle that an agent has selected for interaction. This is usually done within a procedure where you’re trying to move an agent towards or interact with another agent.

  2. Conditional Targeting: You can use logic to define what qualifies as a target. For example, selecting a patch that is a specific color, optimizing behavior for agents such as resource collection, predator/prey interactions, or spatial movements.

  3. Behavioral Implementation: Agents can exhibit complex behaviors by choosing targets based on environmental conditions or internal state.

Example Use Case:

Imagine a model where turtles seek out patches of food to consume:

Summary

  • target: In NetLogo, target is generally used as a variable name to represent a specific agent (patch or turtle) that another agent aims to move toward or interact with.

  • Universal Use: The concept of a “target” is universal and flexible, allowing for dynamic interactions in simulations.

  • Rationale: Helps in creating behaviors like foraging, chasing, avoiding, or territorial control among agents in a simulation.

Ultimately, by using constructs and naming conventions like target, modelers can create more readable and organized code, systematically managing interactions between agents in their simulations. If you have seen target in particular code within a special context, it might be related to such uses.

distance

In NetLogo, the distance function is used to calculate the Euclidean distance between an agent and a given point in the environment. This function is often used when you want agents (like turtles) to measure how far away they are from other agents or patches, which is crucial for behaviors like moving toward a target or determining whether an agent is within a certain range.

Key Characteristics of distance

  1. Euclidean Distance: The distance measured is the straight-line distance in the two-dimensional coordinate space of the NetLogo world, calculated using the Pythagorean theorem.

  2. Syntax: The basic syntax of distance follows this pattern:

    Here, target can be another agent (e.g., a turtle or a patch) or a set of coordinates specified by list x y.

  3. Return Type: The function returns a numeric value representing the distance.

Examples

  • Distance to a Patch:

    This line calculates the distance from the calling turtle to its home patch my-home.

  • Distance to Another Turtle:

    This example finds the nearest other turtle to the calling turtle.

  • Distance to a Point:

    Here, distancexy is a variant used when you have specific coordinates, calculating distance from the current turtle to the point (0, 0).

Practical Uses

  • Navigation and Movement: Determine how far a turtle is from a destination or target, allowing for steering or directed movement.
  • Proximity Checking: Use distance to implement behaviors that depend on turtles being within a certain range, like for interactions, collisions, or field of vision.
  • Optimization and Searching: Calculate distances to decide on optimal paths or when searching for the nearest resources or other agents.

The distance function is a versatile tool in NetLogo, whether you’re simulating natural behaviors, game mechanics, or any scenario requiring spatial awareness and movement dynamics.

Distance Home

When implementing a simulation where movement costs energy, it’s important to clearly define the cost of movement per unit distance. If moving forward 1 costs 1 unit of energy, then you should consider the distance back to their ‘home’ when determining the threshold for starting the return journey.

To calculate when turtles need to start heading home based on their energy, you need to ensure they have enough energy to complete the trip. Here’s how you can determine the appropriate threshold for returning home:

  1. Energy Cost per Movement: If each step (forward 1) costs 1 unit of energy, then each turtle needs at least as much energy as the distance from their current location to their home patch.

  2. Distance Measurement: Use distance my-home to calculate how much energy is needed to move directly back to their home.

  3. Return Threshold: Set the return threshold based on the calculated distance.

Instead of using energy / 2, calculate the distance to their home and start the return trip when the energy is equal to or just greater than that distance:

Considerations:

  • Distance Calculation: The turtles begin returning when their energy is more than the distance back to their home. This ensures they have enough energy to make the trip directly.

  • Energy Management: Adjust the initial energy level and energy loss per movement step to suit your simulation’s goals.

  • Dynamic Behavior: With this setup, turtles dynamically decide when to return, ensuring they don’t run out of energy before reaching their home.

This approach realistically models energy consumption in relation to distance, ensuring turtles anticipate the energy required for returning and don’t risk getting stranded.

It looks like you’re working with NetLogo, a popular agent-based modeling environment. In your code snippet, you are attempting to identify the patch with a particular color (green) that is closest to a certain reference point.

Here’s a corrected version of your code snippet:

A few things to note:

  1. min-one-of: This command is used to find the patch (or turtle) with the minimum value of a given reporter.

  2. patches with [pcolor = green]: This selects all patches that have the desired color, green in this case.

  3. [distance myself]: This calculates the distance from the current turtle or observer to each green patch, allowing min-one-of to choose the one with the smallest distance. Ensure that the command is run in a context where myself is appropriately defined, such as within a turtle or observer context, since distance calculates from the calling agent.

Let me know if you need further clarification or have additional questions!

Face

The error with the face command in your code is caused by an incorrect usage of most-attractive. The max function returns a numeric value (the maximum attractiveness), not an agent (like a turtle or a patch). The face command expects an agent or a pair of coordinates, not a number.

To find and face the most attractive turtle, you need to identify which turtle among the close-turtles has this maximum attractiveness value. Here’s how you can adjust your code:

Key Modifications and Explanation:

  • let close-turtles other turtles in-radius 5: Use other turtles to prevent the turtle from considering itself.

  • Find most-attractive value: First, determine the maximum value of attractiveness among the close-turtles.

  • Identify the target-turtle: Use one-of alongside with to select a turtle (or one of the turtles) whose attractiveness matches most-attractive. This gives you an actual turtle agent to face.

  • face target-turtle: Once you have the target-turtle, you can face it correctly, as it’s now the input type that face expects.

These changes ensure that turtles can identify and face the most attractive neighbor within their local vicinity.

move towards closest turtles

to setup
  clear-all
  create-turtles 40[
    setxy random-xcor random-ycor
  ]
  reset-ticks
end


to go
  ask turtles[
   move
  ]
  
  tick
end

to move
  let close-turtles other turtles in-radius 5
  if any? close-turtles [
    let closest-turtle min-one-of close-turtles [distance myself]
    face closest-turtle
    forward 1
  ]
end

if any?

The NetLogo code you provided has a few issues that could cause it to not work properly. Let’s address these issues step by step:

  1. Syntax Errors:
    • NetLogo requires each instruction in the procedure to be on its own line, or lines can be joined using square brackets. For instance, create-turtles 10 [ setxy random-xcor random-ycor ] is correct, but later you have reset-ticks end to go squeezed together without a line break.
  2. Logical Errors:
    • In the move procedure, you’re defining close-patch and patch-green variables, but the way they’re being used is incorrect. patches in-radius 5 returns an agentset of patches within 5 units of the caller, whereas patches with [pcolor = green] returns an agentset of all green patches.
    • You are trying to use move-to patch-green, which is problematic because patch-green might contain multiple patches, and move-to expects a single patch agent, not an agentset.
  3. Fixing the Move Logic:
    • If you want turtles to move towards the nearest green patch within a certain radius, you have to ensure that there is a green patch present and handle the possibility of multiple patches correctly. You need a decision-making mechanism to choose one patch from the green patches.

Here’s a modified version of the code with corrections:

Key Changes:

  • Line Breaks and Syntax: Ensure proper line breaks between commands for clarity.

  • Logic in move:

    • Define close-patches as patches within a radius of 5 from the turtle, and green-patches as those with a green color within that area.
    • Check if there are any green patches in the vicinity before trying to move-to using if any? green-patches.
    • Use one-of green-patches to randomly select one patch from the set of available green patches within the defined radius.

These changes should help make the code functional in NetLogo and achieve the intended behavior.

in-radius