[英]Python & Matplotlib: How to create a meshgrid to plot surf?
我想绘制一个概率密度函数z=f(x,y)
。 我在使用表面渐变的Color matplotlib plot_surface命令中找到了用于绘制冲浪的代码
但是我不知道如何将z
值转换为grid
因此我可以将其绘制出来示例代码及其修改如下。
import numpy as np
import matplotlib.pyplot as plt
from sklearn import mixture
import matplotlib as mpl
from mpl_toolkits.mplot3d import Axes3D
from matplotlib import cm
%matplotlib inline
n_samples = 1000
# generate random sample, two components
np.random.seed(0)
shifted_gaussian = np.random.randn(n_samples, 2) + np.array([20, 5])
sample = shifted_gaussian
# fit a Gaussian Mixture Model with two components
clf = mixture.GMM(n_components=3, covariance_type='full')
clf.fit(sample)
# Plot it
fig = plt.figure()
ax = fig.gca(projection='3d')
X = np.arange(-5, 5, .25)
Y = np.arange(-5, 5, .25)
X, Y = np.meshgrid(X, Y)
## In example Code, the z is generate by grid
# R = np.sqrt(X**2 + Y**2)
# Z = np.sin(R)
# In my case,
# for each point [x,y], the probability value is
# z = clf.score([x,y])
# but How can I generate a grid Z?
Gx, Gy = np.gradient(Z) # gradients with respect to x and y
G = (Gx**2+Gy**2)**.5 # gradient magnitude
N = G/G.max() # normalize 0..1
surf = ax.plot_surface(
X, Y, Z, rstride=1, cstride=1,
facecolors=cm.jet(N),
linewidth=0, antialiased=False, shade=False)
plt.show()
绘制z
的原始方法是通过网格生成。 但是在我的情况下,拟合模型无法以grid-like
样式返回结果,所以问题是如何生成grid-style z
值并绘制它?
如果我理解正确,您基本上就有一个函数z
,该函数在列表中采用两个标量值x,y
并返回另一个标量z_val
。 换句话说z_val = z([x,y])
,对吗?
如果是这样,您可以执行以下操作(请注意,编写本文时并未考虑效率,而是着重于可读性):
from itertools import product
X = np.arange(15) # or whatever values for x
Y = np.arange(5) # or whatever values for y
N, M = len(X), len(Y)
Z = np.zeros((N, M))
for i, (x,y) in enumerate(product(X,Y)):
Z[np.unravel_index(i, (N,M))] = z([x,y])
如果要使用plot_surface
,请遵循以下步骤:
X, Y = np.meshgrid(X, Y)
ax.plot_surface(X, Y, Z.T)
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