PatchCollection 绘制一个过度缩放的箭头补丁

让我们使用 FancyArrowPatch 在两个散点之间绘制一个箭头：

import matplotlib.pyplot as plt
import matplotlib as mpl

fig, ax  = plt.subplots()

points = ax.scatter([0,1],[0,1], marker='o', s=300)
arrow = mpl.patches.FancyArrowPatch((0,0), (1,1), arrowstyle='-|>', mutation_scale=20)
ax.add_patch(arrow)

fig.show()

Looks OK

现在，让我们使用 PatchCollection 执行相同的绘图

import matplotlib.pyplot as plt
import matplotlib as mpl

fig, ax  = plt.subplots()

points = ax.scatter([0,1],[0,1], marker='o', s=300)
arrow = mpl.patches.FancyArrowPatch((0,0), (1,1), arrowstyle='-|>', mutation_scale=20)
col = mpl.collections.PatchCollection([arrow])
ax.add_collection(col)
fig.show()

Could someone clarify what's happening?

The FancyArrowPatch主要设计用于注释。明显缺乏与其他补丁的兼容性，因此缺乏 PatchCollection。 （正如@tom 在评论中指出的那样，链接到[这个问题]）。

解决方法可能是从箭头路径创建一个新补丁并将该新补丁添加到集合中。这不允许保留所有功能FancyArrowPatch所以最后值得怀疑的是，根本不使用 PatchCollection 是否不是更好的解决方案。

import matplotlib.pyplot as plt
import matplotlib as mpl
import matplotlib.patches as mpatches

fig, ax  = plt.subplots()

points = ax.scatter([0,1],[0,1], marker='o', s=300)
arrow1 = mpatches.FancyArrowPatch((0,0), (1,1), arrowstyle='-|>', mutation_scale=50)
arrow2 = mpatches.FancyArrowPatch((.7,0), (0.1,0), arrowstyle='->', mutation_scale=30)

def arrows2collection(ax, arrows,**kw):
    p = []
    for arrow in arrows:
        ax.add_patch(arrow)
        path = arrow.get_path()
        p.append(mpatches.PathPatch(path,**kw))
        arrow.remove()
    col = mpl.collections.PatchCollection(p,match_original=True)
    ax.add_collection(col)
    return col


col = arrows2collection(ax, [arrow1,arrow2], linewidth=1)


plt.show()