Question

我使用StratifiedShuffleSplit交叉验证器预测波士顿数据集中的房价。当我运行下面的示例代码时。

map.size

我收到以下错误。该代码适用于ShuffleSplit。这意味着StratifiedShuffleSplit不能与数字标签一起使用。

def fit_model_S(labels, features,step, clf,parameters):
  cv = StratifiedShuffleSplit(n_splits=2,test_size=0.10, random_state = 42)
  print (cv)
  for train_index, test_index in cv.split(features,labels):
    labels_train, labels_test = labels[train_index], labels[test_index]
    features_train, features_test = features[train_index], features[test_index]

数据集示例如下。

---------------------------------------------------------------------------
ValueError                                Traceback (most recent call last)
<ipython-input-141-b290147edcbf> in <module>()
     33 dt_steps = [('decision', clf)]
     34 
---> 35 fit_model_S(labels, features,dt_steps,clf,parameters4)  
     36 
     37 

<ipython-input-141-b290147edcbf> in fit_model_S(labels, features, step, clf, parameters)
      8     cv = StratifiedShuffleSplit(n_splits=2,test_size=0.10, random_state = 42)
      9     print (cv)
---> 10     for train_index, test_index in cv.split(features,labels):
     11 
     12         labels_train, labels_test = labels[train_index], labels[test_index]

C:\ProgramData\Anaconda3\lib\site-packages\sklearn\model_selection\_split.py in split(self, X, y, groups)
   1194         """
   1195         X, y, groups = indexable(X, y, groups)
-> 1196         for train, test in self._iter_indices(X, y, groups):
   1197             yield train, test
   1198 

C:\ProgramData\Anaconda3\lib\site-packages\sklearn\model_selection\_split.py in _iter_indices(self, X, y, groups)
   1535         class_counts = np.bincount(y_indices)
   1536         if np.min(class_counts) < 2:
-> 1537             raise ValueError("The least populated class in y has only 1"
   1538                              " member, which is too few. The minimum"
   1539                              " 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.

在这种情况下，MEDV是标签。

Answer 1

Boston Housing数据是回归问题的数据集。您正在使用StratifiedShuffleSplit将其划分为火车和测试。 StratifiedShuffleSplit为mentioned in docs：

这个交叉验证对象是StratifiedKFold和的合并 ShuffleSplit，返回分层随机折叠。折叠是通过保留每个班级的样本百分比来制作。

请查看最后一行： - ＆＃34;保留每个班级的样本百分比＆＃34;。因此，StratifiedShuffleSplit会尝试将y值视为单个类。

但这是不可能的，因为你的y是一个回归变量（连续数值数据）。

请查看ShuffleSplit或train_test_split来划分数据。有关交叉验证的详细信息，请参阅此处：http://scikit-learn.org/stable/modules/cross_validation.html#cross-validation

StratifiedShuffleSplit：ValueError：y中填充最少的类只有1个成员，这个成员太少了。

1 个答案: