使用matplotlib的动画交互式绘图

Question

在寻找使用matplotlib制作动画交互式绘图的方法时，我在Stack溢出文档中遇到了这段代码：

import numpy as np
import matplotlib.pyplot as plt
import matplotlib.animation as animation
from matplotlib.widgets import Slider

TWOPI = 2*np.pi

fig, ax = plt.subplots()

t = np.arange(0.0, TWOPI, 0.001)
initial_amp = .5
s = initial_amp*np.sin(t)
l, = plt.plot(t, s, lw=2)

ax = plt.axis([0,TWOPI,-1,1])

axamp = plt.axes([0.25, .03, 0.50, 0.02])
# Slider
samp = Slider(axamp, 'Amp', 0, 1, valinit=initial_amp)

def update(val):
    # amp is the current value of the slider
    amp = samp.val
    # update curve
    l.set_ydata(amp*np.sin(t))
    # redraw canvas while idle
    fig.canvas.draw_idle()

# call update function on slider value change
samp.on_changed(update)

plt.show()

这段代码几乎完全符合我的要求，但是我希望为绘图设置动画，即让滑块自动从左向右移动，例如每秒进展0.01。有没有简单的方法呢？知道我也想在滑块上保持手动控制（使用点击事件）。

Answer 1

您可以调整this answer中的代码以包含滑块。

import numpy as np
import matplotlib.pyplot as plt
from matplotlib.animation import FuncAnimation
import mpl_toolkits.axes_grid1
import matplotlib.widgets

class Player(FuncAnimation):
    def __init__(self, fig, func, frames=None, init_func=None, fargs=None,
                 save_count=None, mini=0, maxi=100, pos=(0.125, 0.92), **kwargs):
        self.i = 0
        self.min=mini
        self.max=maxi
        self.runs = True
        self.forwards = True
        self.fig = fig
        self.func = func
        self.setup(pos)
        FuncAnimation.__init__(self,self.fig, self.update, frames=self.play(), 
                                           init_func=init_func, fargs=fargs,
                                           save_count=save_count, **kwargs )    

    def play(self):
        while self.runs:
            self.i = self.i+self.forwards-(not self.forwards)
            if self.i > self.min and self.i < self.max:
                yield self.i
            else:
                self.stop()
                yield self.i

    def start(self):
        self.runs=True
        self.event_source.start()

    def stop(self, event=None):
        self.runs = False
        self.event_source.stop()

    def forward(self, event=None):
        self.forwards = True
        self.start()
    def backward(self, event=None):
        self.forwards = False
        self.start()
    def oneforward(self, event=None):
        self.forwards = True
        self.onestep()
    def onebackward(self, event=None):
        self.forwards = False
        self.onestep()

    def onestep(self):
        if self.i > self.min and self.i < self.max:
            self.i = self.i+self.forwards-(not self.forwards)
        elif self.i == self.min and self.forwards:
            self.i+=1
        elif self.i == self.max and not self.forwards:
            self.i-=1
        self.func(self.i)
        self.slider.set_val(self.i)
        self.fig.canvas.draw_idle()

    def setup(self, pos):
        playerax = self.fig.add_axes([pos[0],pos[1], 0.64, 0.04])
        divider = mpl_toolkits.axes_grid1.make_axes_locatable(playerax)
        bax = divider.append_axes("right", size="80%", pad=0.05)
        sax = divider.append_axes("right", size="80%", pad=0.05)
        fax = divider.append_axes("right", size="80%", pad=0.05)
        ofax = divider.append_axes("right", size="100%", pad=0.05)
        sliderax = divider.append_axes("right", size="500%", pad=0.07)
        self.button_oneback = matplotlib.widgets.Button(playerax, label=ur'$\u29CF$')
        self.button_back = matplotlib.widgets.Button(bax, label=ur'$\u25C0$')
        self.button_stop = matplotlib.widgets.Button(sax, label=ur'$\u25A0$')
        self.button_forward = matplotlib.widgets.Button(fax, label=ur'$\u25B6$')
        self.button_oneforward = matplotlib.widgets.Button(ofax, label=ur'$\u29D0$')
        self.button_oneback.on_clicked(self.onebackward)
        self.button_back.on_clicked(self.backward)
        self.button_stop.on_clicked(self.stop)
        self.button_forward.on_clicked(self.forward)
        self.button_oneforward.on_clicked(self.oneforward)
        self.slider = matplotlib.widgets.Slider(sliderax, '', 
                                                self.min, self.max, valinit=self.i)
        self.slider.on_changed(self.set_pos)

    def set_pos(self,i):
        self.i = int(self.slider.val)
        self.func(self.i)

    def update(self,i):
        self.slider.set_val(i)


### using this class is as easy as using FuncAnimation:            

fig, ax = plt.subplots()
x = np.linspace(0,6*np.pi, num=100)
y = np.sin(x)

ax.plot(x,y)
point, = ax.plot([],[], marker="o", color="crimson", ms=15)

def update(i):
    point.set_data(x[i],y[i])

ani = Player(fig, update, maxi=len(y)-1)

plt.show()

Answer 2

以下是对代码添加动画的简单修改：

<script src="https://cdn.jsdelivr.net/npm/signature_pad@2.3.2/dist/signature_pad.min.js"></script>

主要变化是添加了import numpy as np import matplotlib.pyplot as plt import matplotlib.animation as animation from matplotlib.widgets import Slider TWOPI = 2*np.pi fig, ax = plt.subplots() t = np.arange(0.0, TWOPI, 0.001) initial_amp = .5 s = initial_amp*np.sin(t) l, = plt.plot(t, s, lw=2) ax = plt.axis([0,TWOPI,-1,1]) axamp = plt.axes([0.25, .03, 0.50, 0.02]) # Slider samp = Slider(axamp, 'Amp', 0, 1, valinit=initial_amp) # Animation controls is_manual = False # True if user has taken control of the animation interval = 100 # ms, time between animation frames loop_len = 5.0 # seconds per loop scale = interval / 1000 / loop_len def update_slider(val): global is_manual is_manual=True update(val) def update(val): # update curve l.set_ydata(val*np.sin(t)) # redraw canvas while idle fig.canvas.draw_idle() def update_plot(num): global is_manual if is_manual: return l, # don't change val = (samp.val + scale) % samp.valmax samp.set_val(val) is_manual = False # the above line called update_slider, so we need to reset this return l, def on_click(event): # Check where the click happened (xm,ym),(xM,yM) = samp.label.clipbox.get_points() if xm < event.x < xM and ym < event.y < yM: # Event happened within the slider, ignore since it is handled in update_slider return else: # user clicked somewhere else on canvas = unpause global is_manual is_manual=False # call update function on slider value change samp.on_changed(update_slider) fig.canvas.mpl_connect('button_press_event', on_click) ani = animation.FuncAnimation(fig, update_plot, interval=interval) plt.show() 函数，该函数用于在倒数第二行中生成update_plot。动画从设置的最后一个滑块值开始递增。

变量FuncAnimation会跟踪用户点击滑块的时间。用户点击它后，变量设置为is_manual，动画将不再更新绘图。

为了恢复动画，我添加了一个True函数，当用户点击画布上的某个位置而不是滑块时设置on_click。

由于这是一个快速而肮脏的脚本，我将变量保留为全局变量，但您可以轻松地在适当的类中编写它。

请注意，调用is_manual = False会隐式调用samp.set_val函数，当用户直接点击滑块时也会调用该函数，因此我们必须重置update_slider is_manual功能。