如何删除使用滑块小部件添加的 axhline

Question

我从 SO 中提取了以下代码并对其进行了修改以更接近我的需要。基本上，我希望用户移动滑块来更改 axhline 的位置，然后用它来进行计算。我的问题是，应该删除以前的 axhline 的行不会删除它，它会破坏我的功能，并且不会在滑块更改时创建新行。我的 remove() 调用有什么问题？函数终止时对 axhline 的引用是否丢失？我试图让它成为全球性的，但这没有帮助。

    # Import libraries
import numpy as np
import matplotlib.pyplot as plt
from matplotlib.widgets import Slider, Button
%matplotlib notebook

# Create a subplot
fig, ax = plt.subplots()
plt.subplots_adjust(bottom=0.35)
r = 0.6
g = 0.2
b = 0.5

# Create and plot a bar chart
year = [2002, 2004, 2006, 2008, 2010]
production = [25, 15, 35, 30, 10]
plt.bar(year, production, color=(r, g, b))
targ_line = plt.axhline(y=20, xmin=-.1, clip_on=False, zorder=1, color='#e82713')

# Create 3 axes for 3 sliders red,green and blue
target = plt.axes([0.25, 0.2, 0.65, 0.03])


# Create a slider from 0.0 to 35.0 in axes target
# with 20.0 as initial value.
red = Slider(target, 'Target', 0.0, 35.0, 20)


# Create fuction to be called when slider value is changed
# This is the part I am having trouble with.  I want to remove the previous line
# so that there will only be one axhline present

def update(val):  
    #targ_line.remove()   # uncommenting this line doesn't remove the line and prevents the remainder of the code in this function from running.
    Y = red.val
    targ_line = ax.axhline(y=Y, color = 'black')
    ax.bar(year, production, color=(r, g, b),
        edgecolor="black")

# Call update function when slider value is changed
red.on_changed(update)


# Create axes for reset button and create button
resetax = plt.axes([0.8, 0.025, 0.1, 0.04])
button = Button(resetax, 'Reset', color='gold',
                hovercolor='skyblue')

# Create a function resetSlider to set slider to
# initial values when Reset button is clicked

def resetSlider(event):
        red.reset()


# Call resetSlider function when clicked on reset button
button.on_clicked(resetSlider)

# Display graph
plt.show()

Answer 1

您可以尝试更新 axhline 而不是重新创建它。例如：

def update(val):  
    #Y = red.val
    #targ_line = ax.axhline(y=Y, color = 'black')
    targ_line.set_ydata(y=red.val)
    targ_line.set_color('black')
    ax.bar(year, production, color=(r, g, b), edgecolor="black")

如何删除使用滑块小部件添加的 axhline

How can I remove the axhline I added with my slider widget

plot

bar-chart

python-3.x

matplotlib-widget