python - Matplotlib:带有 slider 小部件的等高线图

Question

这里是新手 matplotlib 用户。我正在尝试使用 slider 调整等高线图中的参数，但是当我这样做时，我得到:

AttributeError: QuadContourSet instance has no attribute 'set_data'

我怀疑我在错误的对象上调用了 set_data，但我找不到关于正确 对象是什么的任何文档。你能帮我吗？谢谢。

完整代码如下:

import numpy as np
import matplotlib as mpl
import matplotlib.mlab as mlab
import matplotlib.pyplot as pyl
from matplotlib.contour import QuadContourSet
from matplotlib.widgets import Slider

#Define display parameters
mpl.rcParams['xtick.direction'] = 'out'
mpl.rcParams['ytick.direction'] = 'out'
delta = 0.025

#Define model parameters
alpha = .5
beta = .5
x_bar, a, b, c = 2, 0, 1, .1
v = np.arange(0, 10, delta)
w = np.arange(0, 10, delta)

#Calculate grid values
V, W = np.meshgrid(v,w)
Z = (V**(beta))*(W**(1-beta))
X = x_bar + a + b*Z
U = alpha*np.log(V) + (1-alpha)*np.log(X) - c*(W+V)

# Plot
fig = pyl.figure()

ax = fig.add_subplot(221)
CS = QuadContourSet(pyl.gca(), V, W, U, 200)
pyl.clabel(CS, inline=1, fontsize=10)
pyl.title('Simplest default with labels')

#Define slider for alpha
axcolor = 'lightgoldenrodyellow'
alpha_axis  = pyl.axes([0.25, 0.15, 0.65, 0.03], axisbg=axcolor)
alpha_slider = Slider(alpha_axis, 'Amp', 0, 1, valinit=.5)

def update(val):
    alpha = alpha_slider.val
    U = alpha*np.log(V) + (1-alpha)*np.log(X) - c*(W+V)
    CS.set_data(V, W, U)
    pyl.draw()

alpha_slider.on_changed(update)

pyl.show()

Answer 1

问题是 QuadContourSet 对象没有办法更新它的数据，因为如果你任意改变数据，整个事情都需要重新计算。我不知道你生成数据的特殊方式是否有一些东西可以用来更简单地修改等高线，但如果没有，我认为你需要做的是从头开始绘制等高线:

# After your "Define model parameters" block

def compute_and_plot(ax, alpha):
    #Calculate grid values
    V, W = np.meshgrid(v,w)
    Z = (V**(beta))*(W**(1-beta))
    X = x_bar + a + b*Z
    U = alpha*np.log(V) + (1-alpha)*np.log(X) - c*(W+V)

    CS = QuadContourSet(ax, V, W, U, 200)
    pyl.clabel(CS, inline=1, fontsize=10)

# Plot
fig = pyl.figure()
pyl.title('Simplest default with labels')
ax = fig.add_subplot(221)
compute_and_plot(ax, alpha)

#Define slider for alpha
axcolor = 'lightgoldenrodyellow'
alpha_axis  = pyl.axes([0.25, 0.15, 0.65, 0.03], axisbg=axcolor)
alpha_slider = Slider(alpha_axis, 'Amp', 0, 1, valinit=.5)

def update(ax, val):
    alpha = alpha_slider.val
    ax.cla()
    compute_and_plot(ax, alpha)
    pyl.draw()

alpha_slider.on_changed(lambda val: update(ax, val))

pyl.show()