使用 MNIST 样本可视化每个数字的 10x10 网格

Question

我正在尝试从 MNIST 数据集中绘制 10x10 网格样本。每个数字 10 个。这是代码：

导入库：

import sklearn
import numpy as np
import matplotlib.pyplot as plt
from matplotlib.ticker import MultipleLocator
from sklearn.pipeline import Pipeline
from sklearn.datasets import fetch_openml

加载数字数据：

X, Y = fetch_openml(name='mnist_784', return_X_y=True, cache=False)

绘制网格：

def P1(num_examples=10):
plt.rc('image', cmap='Greys')
plt.figure(figsize=(num_examples,len(np.unique(Y))), dpi=X.shape[1])
# For each digit (from 0 to 9)
for i in np.nditer(np.unique(Y)):
    # Create a ndarray with the features of "num_examples" examples of digit "i"
    features = X[Y == i][:num_examples]
    # For each of the "num_examples" examples
    for j in range(num_examples):
        # Create subplot (from 1 to "num_digits"*"num_examples" of each digit)
        plt.subplot(len(np.unique(Y)), num_examples, i * num_examples + j + 1)
        plt.subplots_adjust(wspace=0, hspace=0)
        # Hide tickmarks and scale
        ax = plt.gca()
        # ax.set_axis_off() # Also hide axes (frame) 
        ax.axes.get_xaxis().set_visible(False)
        ax.axes.get_yaxis().set_visible(False)
        # Plot the corresponding digit (reshaped to square matrix/image)
        dim = int(np.sqrt(X.shape[1]))
        digit = features[j].reshape((dim,dim))            
        plt.imshow(digit)
P1(10)

但是，我在这里收到一条错误消息："Iterator operand or requested dtype holds references, but the REFS_OK flag was not enabled"

谁能帮我解决这个问题？

Answer 1

此错误很可能来自 nd.iter，您不需要 - 还建议使用 subplots 和 ax 而不是 MATLAB 样式 plt 调用：

digits = np.unique(Y)
M = 10
dim = int(np.sqrt(X.shape[1]))

fig, axs = plt.subplots(len(digits), M, figsize=(20,20))

for i,d in enumerate(digits):
    for j in range(M):
        axs[i,j].imshow(X[Y==d][j].reshape((dim,dim)))
        axs[i,j].axis('off')

使用 MNIST 样本可视化每个数字的 10x10 网格

visualize 10x10 grid of each digit using MNIST samples

python-3.x

scikit-learn

mnist