Matplotlib 地图多图例定制：整合色块与符号标记

import matplotlib.pyplot as plt
from matplotlib.patches import Patch
import matplotlib.lines as mlines # 导入但未用于原始图例

# 假设 color_list 已定义，用于生成区域色块图例
patches = []
for category, color in color_list.items():
    patch = Patch(color=color, label=category)
    patches.append(patch)

# 假设 sao 和 asset 是 GeoDataFrame，ax 是 Matplotlib 轴对象
# sao.plot(...) # 绘制区域
# asset.plot(color='black', markersize = 110, marker= "$x$", ax=ax, label = "assets")

# 原始的图例创建方式，问题在于资产图例项
plt.legend(handles=patches + [Patch(color='black', label="assets")], loc='lower right', title = 'Crime Rate Level for Districts')
plt.show()

from matplotlib.lines import Line2D

# ... (假设 patches 已经按照上述方式创建) ...

# 为资产点创建 Line2D 图例项
asset_legend_handle = Line2D(
    [], [],               # 空列表表示没有实际数据点，仅用于图例
    marker='x',           # 指定标记样式为 'x'
    linestyle='',         # 不显示线条
    color='black',        # 标记颜色
    markersize=10,        # 标记大小，可根据图中实际标记大小调整
    label="Assets"        # 图例标签
)

# 整合所有图例项：色块图例和 Line2D 标记图例
plt.legend(
    handles=patches + [asset_legend_handle],
    loc='lower right',
    title='Risk Areas - São Paulo, Brazil'
)

import matplotlib.pyplot as plt
from matplotlib.patches import Patch
from matplotlib.lines import Line2D
import pandas as pd
import geopandas as gpd
from shapely.geometry import Polygon, Point

# --- 模拟数据 ---
# 模拟犯罪率区域及颜色
color_list = {
    'Low Risk': 'green',
    'Medium Risk': 'orange',
    'High Risk': 'red'
}

# 模拟区域几何数据 (简化为矩形)
data = {
    'district': ['A', 'B', 'C'],
    'geometry': [
        Polygon([(0, 0), (0, 1), (1, 1), (1, 0), (0, 0)]),
        Polygon([(1, 1), (1, 2), (2, 2), (2, 1), (1, 1)]),
        Polygon([(2, 2), (2, 3), (3, 3), (3, 2), (2, 2)])
    ],
    'Colors': ['green', 'orange', 'red'] # 对应color_list
}
sao = gpd.GeoDataFrame(data, geometry='geometry')

# 模拟资产点
asset_data = {'geometry': [Point(0.5, 0.5), Point(1.5, 1.5)]}
asset = gpd.GeoDataFrame(asset_data, geometry='geometry')

# --- 绘图部分 ---
fig, ax = plt.subplots(figsize=(10, 8))

# 绘制区域
sao.plot(color=sao["Colors"], ax=ax, edgecolor='black', linewidth=0.5)

# 绘制资产点
asset.plot(color='black', markersize=200, marker="$x$", ax=ax, label="assets")

# 创建区域风险等级的图例项 (Patch)
patches = []
for category, color in color_list.items():
    patch = Patch(color=color, label=category)
    patches.append(patch)

# --- 解决方案：使用 Line2D 创建资产点的图例项 ---
asset_legend_handle = Line2D(
    [], [],
    marker='x',         # 使用 'x' 标记
    linestyle='',       # 不显示线条
    color='black',      # 标记颜色
    markersize=10,      # 标记大小 (可以调整以匹配图中实际大小)
    label="Assets"      # 图例标签
)

# 整合所有图例项
plt.legend(
    handles=patches + [asset_legend_handle],
    loc='lower right',
    title='Risk Areas - São Paulo, Brazil'
)

# 设置标题和移除坐标轴
ax.set_title('Risk Areas - São Paulo, Brazil', fontweight='bold')
ax.axis('off')

plt.show()