Matplotlib:带有滑块小部件的等高线图

2022-01-24 00:00:00 python matplotlib slider

问题描述

新手 matplotlib 用户在这里.我正在尝试使用滑块来调整等高线图中的参数，但是当我这样做时，我得到:

Newbie matplotlib user here. I'm trying to use a slider to adjust a parameter in a contour plot, but when I do so, I get:

AttributeError: QuadContourSet instance has no attribute 'set_data'

我怀疑我在错误的对象上调用 set_data，但我找不到任何关于 right 对象是什么的文档.你能帮我吗?谢谢.

I suspect that I'm calling set_data on the wrong object, but I can't find any documentation on what the right object is. Can you help? Thanks.

这是完整的代码:

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()

解决方案

问题是 QuadContourSet 对象没有办法更新它的数据，因为如果你随意更改数据，整个事情都需要重新计算.我不知道您生成数据的特定方式是否有助于以更简单的方式修改等高线，但如果没有，我认为您需要做的是从头开始绘制等高线:

The problem is that the QuadContourSet object has no way to update its data, since if you change the data arbitrarily, the whole thing needs to be recomputed. I don't know if there is something about your particular way of generating data that would lend itself to a simpler way to modify the contour lines, but if not, I think what you need to do is to plot the contours from scratch:

# 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()

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