发生鼠标悬停事件时如何更改饼图的颜色

Question

我在matplotlib 中创建了一个饼图。我想在 python 中实现this 结果，即每当鼠标悬停在任何切片上时，它的颜色都会改变。我进行了很多搜索并想出了使用bind 方法，但这虽然无效，因此无法提出积极的意见结果。如果这可以通过任何其他库完成，我将没有问题（比如tkinter、plotly 等，但我需要用matplotlib 提出解决方案，所以我会很感激）。请看看通过我的问题，任何建议都受到热烈欢迎...... 这是我的代码：

import matplotlib.pyplot as plt

labels = 'A', 'B', 'C', 'D'
sizes = [10, 35, 50, 5]
explode = (0, 0, 0.1, 0)  # only "explode" the 3rd slice (i.e. 'C')

fig1, ax1 = plt.subplots()
ax1.pie(sizes, explode=explode, labels=labels, autopct='%1.1f%%',
    shadow=True, startangle=90)
ax1.axis('equal')  # Equal aspect ratio ensures that pie is drawn as a circle.

plt.show()

问候...

Answer 1

matplotlib event handler 需要 motion_notify_event。 这可以连接到一个函数，该函数检查鼠标是否在饼图的楔形之一内。这是通过contains_point 完成的。在这种情况下，对楔形进行不同的着色，否则将其颜色设置为其原始颜色。

import matplotlib.pyplot as plt

labels = 'A', 'B', 'C', 'D'
sizes = [10, 35, 50, 5]
explode = (0, 0, 0.1, 0)  # only "explode" the 3rd slice (i.e. 'C')

fig1, ax1 = plt.subplots()
wedges, _, __ = ax1.pie(sizes, explode=explode, labels=labels, autopct='%1.1f%%',
    shadow=True, startangle=90)
ax1.axis('equal')  # Equal aspect ratio ensures that pie is drawn as a circle.

ocols= [w.get_facecolor() for w in wedges]
ncols= ["gold", "indigo", "purple", "salmon"]

def update(event):
    if event.inaxes == ax1:
        for i, w in enumerate(wedges):
            if w.contains_point([event.x, event.y]):
                w.set_facecolor(ncols[i])
            else:
                w.set_facecolor(ocols[i])
        fig1.canvas.draw_idle()


fig1.canvas.mpl_connect("motion_notify_event", update)

plt.show()

Answer 2

首先，您要查找的是the documentation on Event handling in matplotlib。特别是，每次鼠标移动时都会触发motion_notify_event。但是，我想不出一个简单的方法来识别鼠标现在在哪个楔子上。

如果点击是可以接受的，那么问题就简单多了：

labels = 'A', 'B', 'C', 'D'
sizes = [10, 35, 50, 5]
explode = (0, 0, 0.1, 0)  # only "explode" the 3rd slice (i.e. 'C')
click_color = [0.2, 0.2, 0.2]

fig1, ax1 = plt.subplots()
patches, texts, autotexts = ax1.pie(sizes, explode=explode, labels=labels, autopct='%1.1f%%',
    shadow=True, startangle=90)

# store original color inside patch object
# THIS IS VERY HACKY.
# We use the Artist's 'gid' which seems to be unused as far as I can tell
# to be able to recall the original color
for p in patches:
    p.set_gid(p.get_facecolor())
    # enable picking
    p.set_picker(True)

ax1.axis('equal')  # Equal aspect ratio ensures that pie is drawn as a circle.


def on_pick(event):
    #restore all facescolor to erase previous changes
    for p in patches:
        p.set_facecolor(p.get_gid())
    a = event.artist
    # print('on pick:', a, a.get_gid())
    a.set_facecolor(click_color)
    plt.draw()

fig1.canvas.mpl_connect('pick_event', on_pick)
plt.show()