我正在使用带有scikit-learn封装器的Keras。特别地,我想使用GridSearchCV进行超参数优化。
这是一个多类问题,即目标变量只能在n个类集合中选择一个标签。例如,目标变量可以是'Class1','Class2' ... 'Classn'。
# self._arch creates my model
nn = KerasClassifier(build_fn=self._arch, verbose=0)
clf = GridSearchCV(
nn,
param_grid={ ... },
# I use f1 score macro averaged
scoring='f1_macro',
n_jobs=-1)
# self.fX is the data matrix
# self.fy_enc is the target variable encoded with one-hot format
clf.fit(self.fX.values, self.fy_enc.values)
问题在于,在交叉验证期间计算分数时,验证样本的真实标签被编码为one-hot,而由于某种原因,预测结果会折叠为二进制标签(当目标变量仅有两个类别时)。例如,以下是堆栈跟踪的最后一部分:
...........................................................................
/Users/fbrundu/.pyenv/versions/3.6.0/lib/python3.6/site-packages/sklearn/metrics/classification.py in _check_targets(y_true=array([[ 0., 1.],
[ 0., 1.],
[ 0... 0., 1.],
[ 0., 1.],
[ 0., 1.]]), y_pred=array([1, 1, 1, 1, 1, 1, 1, 0, 0, 1, 0, 1, 1, 1,...0, 1, 0, 0, 1, 0, 0, 0,
0, 0, 0, 0, 1, 1]))
77 if y_type == set(["binary", "multiclass"]):
78 y_type = set(["multiclass"])
79
80 if len(y_type) > 1:
81 raise ValueError("Can't handle mix of {0} and {1}"
---> 82 "".format(type_true, type_pred))
type_true = 'multilabel-indicator'
type_pred = 'binary'
83
84 # We can't have more than one value on y_type => The set is no more needed
85 y_type = y_type.pop()
86
ValueError: Can't handle mix of multilabel-indicator and binary
我应该如何指示Keras/sklearn以one-hot编码返回预测结果?
fy
而不对值进行编码时会发生什么。在多类问题中,这不应该是一个问题。在我看来,目标的一位有效编码仅在多标签问题中是必要的。 - Vivek Kumar