python - 为什么图形大小(y 轴)在此示例中波动？

Question

我有一张世界地图，我在 for 循环中迭代地绘制干旱区域。

为了可重复性，数据在这里:https://data.humdata.org/dataset/global-droughts-events-1980-2001

import pandas as pd
import geopandas as gpd

import matplotlib.pyplot as plt
import seaborn as sns

from IPython.display import clear_output
sns.set_theme(style='whitegrid')

dr_geometry = gpd.read_file('data/dr_events.shp')
world_geometry = gpd.read_file(gpd.datasets.get_path('naturalearth_lowres'))

for y in dr_geometry.year.unique():
    clear_output(wait=True)
    fig, ax = plt.subplots(1, 1, figsize=(15, 15))
    world_geometry.plot(ax=ax)
    dr_geometry[dr_geometry.year == y].plot(ax=ax, color='red', edgecolor='black', linewidth=0.1)
    plt.show();
    

这工作正常，除了 y 轴在每次迭代中收缩或扩展一个很小但非常明显的量，导致动画断断续续。我怎样才能消除这种行为？

注意:明确设置 ylim 不会改变这一点。我还尝试将 subplots 实例移到 for 循环之外，但这会导致输出为空。

迭代输出:

Answer 1

ax.set_aspect('equal') 阻止了我这边的移动:

for y in dr_geometry.year.unique():
    clear_output(wait=True)
    fig, ax = plt.subplots(1, 1, figsize=(15, 15))
    world_geometry.plot(ax=ax)
    dr_geometry[dr_geometry.year == y].plot(ax=ax, color='red', edgecolor='black', linewidth=0.1)
    
    # set aspect ratio explicitly
    ax.set_aspect('equal')
    
    plt.show();

---

感谢@martinfleis指出转移的原因:

• geopandas#1121 - Consider scaling y-axis for unprojected map plots
• geopandas#1290 - ENH: scaling y-axis for plots in geographic CRS

.plot() now automatically determines whether GeoSeries (or GeoDataFrame) is in geographic or projected CRS and calculates aspect for geographic using 1/cos(s_y * pi/180) with s_y as the y coordinate of the mean of y-bounds of GeoSeries. This leads to better representation of the actual shapes than current hard-coded 'equal' aspect.