# 交叉驗證：
#matplotlib inline
from sklearn import datasets
from sklearn.model_selection import train_test_split, cross_val_score
from sklearn.neighbors import KNeighborsClassifier
import matplotlib.pyplot as plt
iris = datasets.load_iris()
X = iris.data
y = iris.target
X_train, X_test, y_train, y_test = train_test_split(X, y, test_size=1 / 3., random_state=10)
k_range = range(1, 31)
cv_scores = []
for n in k_range:
knn = KNeighborsClassifier(n)
scores = cross_val_score(knn, X_train, y_train, cv=10, scoring='accuracy') # 分類問題使用
cv_scores.append(scores.mean())
plt.plot(k_range, cv_scores)
plt.xlabel('K')
plt.ylabel('Accuracy')
plt.show()
運行后：
Traceback (most recent call last):
File "F:/PyCharm Community Edition 2020.1/Microsoft Office編程/PDF檔案操作/機器學習-AI.py", line 75, in <module>
import matplotlib.pyplot as plt
File "F:\Python\Python3.7.7\lib\matplotlib\pyplot.py", line 32, in <module>
import matplotlib.colorbar
File "F:\Python\Python3.7.7\lib\matplotlib\colorbar.py", line 27, in <module>
import matplotlib.artist as martist
File "F:\Python\Python3.7.7\lib\matplotlib\artist.py", line 13, in <module>
from .path import Path
File "F:\Python\Python3.7.7\lib\matplotlib\path.py", line 17, in <module>
from . import _path, cbook, rcParams
ImportError: cannot import name '_path' from 'matplotlib' (F:\Python\Python3.7.7\lib\matplotlib\__init__.py)
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