Python sklearn 值错误目标变量

Question

我运行以下代码：

from sklearn.model_selection import train_test_split

X_train,X_test, y_train, y_test=train_test_split(X,y,stratify=y,test_size=0.3)

输出：

---------------------------------------------------------------------------
ValueError                                Traceback (most recent call last)
<ipython-input-27-b5740f8ae579> in <module>()
      1 from sklearn.model_selection import train_test_split
      2 
----> 3 X_train,X_test, y_train, y_test=train_test_split(X,y,stratify=y,test_size=0.3)

/Applications/anaconda3/lib/python3.6/site-packages/sklearn/model_selection/_split.py in train_test_split(*arrays, **options)
   2054                      random_state=random_state)
   2055 
-> 2056         train, test = next(cv.split(X=arrays[0], y=stratify))
   2057 
   2058     return list(chain.from_iterable((safe_indexing(a, train),

/Applications/anaconda3/lib/python3.6/site-packages/sklearn/model_selection/_split.py in split(self, X, y, groups)
   1202         """
   1203         X, y, groups = indexable(X, y, groups)
-> 1204         for train, test in self._iter_indices(X, y, groups):
   1205             yield train, test
   1206 

/Applications/anaconda3/lib/python3.6/site-packages/sklearn/model_selection/_split.py in _iter_indices(self, X, y, groups)
   1544         class_counts = np.bincount(y_indices)
   1545         if np.min(class_counts) < 2:
-> 1546             raise ValueError("The least populated class in y has only 1"
   1547                              " member, which is too few. The minimum"
   1548                              " number of groups for any class cannot"

ValueError: The least populated class in y has only 1 member, which is too few. The minimum number of groups for any class cannot be less than 2.

当我运行使用不同数据的另一个机器学习项目的完全相同的一组行时，它工作正常。我做错了什么？

与正在考虑的数据框形状相关的其他信息：

print(data.shape)
print(X.shape)
print(y.shape)

输出：

(3047, 33)
(3047, 32)
(3047, 1)

Answer 1

由于您正在使用分层，属于每个 class 的样本数量需要在训练和测试中成比例。但是你的数据中有一个 class 只有一个样本。因此，无论是在训练中还是一次测试，这都会破坏分层选项。因此错误。

请参阅我的另一篇文章，其中描述了类似情况的示例。

Python sklearn 值错误目标变量

Python sklearn Value Error Target Variable

python-3.x

scikit-learn

valueerror