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| import mesa | |
| 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 MoneyAgent(mesa.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 = self.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_agent = self.random.choice(cellmates) | |
| other_agent.wealth += 1 | |
| self.wealth -= 1 | |
| def step(self): | |
| self.move() | |
| if self.wealth > 0: | |
| self.give_money() | |
| class MoneyModel(mesa.Model): | |
| """A model with some number of agents.""" | |
| def __init__(self, N, width, height): | |
| self.num_agents = N | |
| self.grid = mesa.space.MultiGrid(width, height, True) | |
| self.schedule = mesa.time.RandomActivation(self) | |
| # 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 = self.random.randrange(self.grid.width) | |
| y = self.random.randrange(self.grid.height) | |
| self.grid.place_agent(a, (x, y)) | |
| def step(self): | |
| self.datacollector.collect(self) | |
| self.schedule.step() | |
| 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 = mesa.visualization.CanvasGrid(agent_portrayal, 10, 10, 500, 500) | |
| server = mesa.visualization.ModularServer( | |
| MoneyModel, [grid], "Money Model", {"N": 100, "width": 10, "height": 10} | |
| ) | |
| chart = mesa.visualization.ChartModule([{"Label": "Gini", | |
| "Color": "Black"}], | |
| data_collector_name='datacollector') | |
| server = mesa.visualization.ModularServer(MoneyModel, | |
| [grid, chart], | |
| "Money Model", | |
| {"N":100, "width":10, "height":10}) | |
| server.port = 7860 | |
| if __name__ == "__main__": | |
| server.launch() |