Reformatting ColorPatches to color_patches and adding money model files.

examples/boltzmann_wealth_model/money_model.py

@@ -0,0 +1,70 @@
+import random
+
+from mesa import Agent, Model
+from mesa.time import RandomActivation
+from mesa.space import MultiGrid
+from mesa.datacollection import DataCollector
+
+
+def compute_gini(model):
+    agent_wealths = [agent.wealth for agent in model.schedule.agents]
+    x = sorted(agent_wealths)
+    N = model.num_agents
+    B = sum(xi * (N - i) for i, xi in enumerate(x)) / (N * sum(x))
+    return (1 + (1 / N) - 2 * B)
+
+
+class MoneyModel(Model):
+    """A model with some number of agents."""
+
+    def __init__(self, N, width, height):
+        self.num_agents = N
+        self.running = True
+        self.grid = MultiGrid(height, width, True)
+        self.schedule = RandomActivation(self)
+        self.datacollector = DataCollector(
+            model_reporters={"Gini": compute_gini},
+            agent_reporters={"Wealth": lambda a: a.wealth}
+        )
+        # Create agents
+        for i in range(self.num_agents):
+            a = MoneyAgent(i, self)
+            self.schedule.add(a)
+            # Add the agent to a random grid cell
+            x = random.randrange(self.grid.width)
+            y = random.randrange(self.grid.height)
+            self.grid.place_agent(a, (x, y))
+
+    def step(self):
+        self.datacollector.collect(self)
+        self.schedule.step()
+
+    def run_model(self, n):
+        for i in range(n):
+            self.step()
+
+
+class MoneyAgent(Agent):
+    """ An agent with fixed initial wealth."""
+    def __init__(self, unique_id, model):
+        super().__init__(unique_id, model)
+        self.wealth = 1
+
+    def move(self):
+        possible_steps = self.model.grid.get_neighborhood(
+            self.pos, moore=True, include_center=False
+        )
+        new_position = random.choice(possible_steps)
+        self.model.grid.move_agent(self, new_position)
+
+    def give_money(self):
+        cellmates = self.model.grid.get_cell_list_contents([self.pos])
+        if len(cellmates) > 1:
+            other = random.choice(cellmates)
+            other.wealth += 1
+            self.wealth -= 1
+
+    def step(self):
+        self.move()
+        if self.wealth > 0:
+            self.give_money()

examples/boltzmann_wealth_model/viz_money_model.py

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+from mesa.visualization.modules import CanvasGrid
+from mesa.visualization.modules import ChartModule
+from mesa.visualization.ModularVisualization import ModularServer
+
+from money_model import MoneyModel
+
+
+def agent_portrayal(agent):
+    portrayal = {"Shape": "circle",
+                 "Filled": "true",
+                 "r": 0.5}
+
+    if agent.wealth > 0:
+        portrayal["Color"] = "red"
+        portrayal["Layer"] = 0
+    else:
+        portrayal["Color"] = "grey"
+        portrayal["Layer"] = 1
+        portrayal["r"] = 0.2
+    return portrayal
+
+grid = CanvasGrid(agent_portrayal, 10, 10, 500, 500)
+chart = ChartModule([
+    {"Label": "Gini", "Color": "Black"}],
+    data_collector_name='datacollector'
+)
+
+server = ModularServer(MoneyModel, [grid, chart], "Money Model", 100, 10, 10)
+server.port = 8521
+server.launch()