Python中的sklearn--KFold与StratifiedKFold

KFold划分数据集的原理：根据n_split直接进行划分

StratifiedKFold划分数据集的原理：划分后的训练集和验证集中类别分布尽量和原数据集一样

#导入相关packages

from sklearn.model_selection import KFold
from sklearn.model_selection import StratifiedKFold

 1 import numpy as np
 2 from sklearn.model_selection import StratifiedKFold
 3 X = np.array([[1, 2], [3, 4], [1, 2], [3, 4]])
 4 y = np.array([0, 0, 1, 1])
 5 skf = StratifiedKFold(n_splits=2)
 6 skf.get_n_splits(X, y)
 7 >>>2
 8 print(skf)
 9 StratifiedKFold(n_splits=2, random_state=None, shuffle=False)
10 for train_index, test_index in skf.split(X, y):
11     print("TRAIN:", train_index, "TEST:", test_index)
12     X_train, X_test = X[train_index], X[test_index]    #返回数据框的方法 X_train = X.iloc[train_index]
13     y_train, y_test = y[train_index], y[test_index]
14 >>>TRAIN: [1 3] TEST: [0 2] #返回的是索引
15 >>>TRAIN: [0 2] TEST: [1 3]