如何在matplotlib中制作两个滑块 [英] How to make two sliders in matplotlib

问题描述

我想在matplotlib中制作两个滑块来手动更改捕食者-猎物模型中的N和P值:

I would like to make two sliders in matplotlib to manually change N and P values in my predator-prey model:

import numpy as np
import matplotlib.pyplot as plt
from scipy.integrate import odeint

def lotka(x,t,params):
    N, P = x 
    alpha, beta, gamma, delta = params 
    derivs = [alpha*N - beta*N*P, gamma*N*P - delta*P] 
    return derivs

N=2
P=1
alpha=3
beta=0.5
gamma=0.4
delta=3

params = [alpha, beta, gamma, delta]
x0=[N,P]
maxt = 20
tstep = 0.01

t=np.arange(0,maxt,tstep)
equation=odeint(lotka, x0, t, args=(params,))

plt.plot(t,equation)
plt.xlabel("Time")
plt.ylabel("Population size")
plt.legend(["Prey", "Predator"], loc="upper right")

plt.title('Prey & Predator Static Model')
plt.grid(color="b", alpha=0.5, linestyle="dashed", linewidth=0.5)

这是我的代码，它为N和P的固定初始值生成图形.但是，我想更改它们以查看曲线图如何变化.为此，我想使用滑块，如:http://matplotlib.org/users/screenshots.html#slider-demo 但我不知道如何将其添加到我的代码中...

This is my code which produces a graph for fixed initial values of N and P. However, I'd like to change them to see how the plot changes. And for this, I'd like to use sliders like: http://matplotlib.org/users/screenshots.html#slider-demo but I do not know how to add this into my code...

有人可以给我任何指示吗?非常感谢！！xx

Could anyone please give me any direction? Many thanks!! xx

推荐答案

从例子中，希望评论能帮助你理解什么是什么:

From the example, hope the comments help you understand what's what:

import numpy as np
import matplotlib.pyplot as plt
from matplotlib.widgets import Slider, Button, RadioButtons
from scipy.integrate import odeint

# Function to draw
def lotka(x, t, params):
    N, P = x
    alpha, beta, gamma, delta = params 
    derivs = [alpha*N - beta*N*P, gamma*N*P - delta*P] 
    return derivs

# Parameters
Nmin = 1
Nmax = 100
Pmin = 1
Pmax = 100
N0 = 2
P0 = 1
alpha = 3
beta = 0.5
gamma = 0.4
delta = 3

params = [alpha, beta, gamma, delta]
x0=[N0,P0]
maxt = 20
tstep = 0.01

# Initial function values
t = np.arange(0, maxt, tstep)
prey, predator = odeint(lotka, x0, t, args=(params,)).T
# odeint returne a shape (2000, 2) array, with the value for
# each population in [[n_preys, n_predators], ...]
# The .T at the end transponses the array, so now we get each population
# over time in each line of the resultint (2, 2000) array.

# Create a figure and an axis to plot in:
fig = plt.figure()
ax = fig.add_axes([0.10, 0.3, 0.8, 0.6])
prey_plot = ax.plot(t, prey, label="Prey")[0]
predator_plot = ax.plot(t, predator, label="Predator")[0]

ax.set_xlabel("Time")
ax.set_ylabel("Population size")
ax.legend(loc="upper right")
ax.set_title('Prey & Predator Static Model')
ax.grid(color="b", alpha=0.5, linestyle="dashed", linewidth=0.5)
ax.set_ylim([0, np.max([prey, predator])])

# create a space in the figure to place the two sliders:
axcolor = 'lightgoldenrodyellow'
axis_N = fig.add_axes([0.10, 0.1, 0.8, 0.03], facecolor=axcolor)
axis_P = fig.add_axes([0.10, 0.15, 0.8, 0.03], facecolor=axcolor)
# the first argument is the rectangle, with values in percentage of the figure
# size: [left, bottom, width, height]

# create each slider on its corresponding place:
slider_N = Slider(axis_N, 'N', Nmin, Nmax, valinit=N0)
slider_P = Slider(axis_P, 'P', Pmin, Pmax, valinit=P0)

def update(val):
    # retrieve the values from the sliders
    x = [slider_N.val, slider_P.val]
    # recalculate the function values
    prey, predator = odeint(lotka, x, t, args=(params,)).T
    # update the value on the graph
    prey_plot.set_ydata(prey)
    predator_plot.set_ydata(predator)
    # redraw the graph
    fig.canvas.draw_idle()
    ax.set_ylim([0, np.max([prey, predator])])

# set both sliders to call update when their value is changed:
slider_N.on_changed(update)
slider_P.on_changed(update)

# create the reset button axis (where its drawn)
resetax = plt.axes([0.8, 0.025, 0.1, 0.04])
# and the button itself
button = Button(resetax, 'Reset', color=axcolor, hovercolor='0.975')

def reset(event):
    slider_N.reset()
    slider_P.reset()

button.on_clicked(reset)

但是请注意，您应该展示您如何尝试使示例适应您所拥有的内容以及如何行为不端.

Notice, however, you should have shown how you tried to adapt the example to what you had and how it was misbehaving.

不过，欢迎使用 Stackoverflow.

Nevertheless, welcome to Stackoverflow.

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