改进布鲁诺的答案,大多数人真正想做的是能够传递任何分类器(不必对每个分类器进行硬编码)以及每个分类器的任何参数。这是一个简单的方法来做到这一点:
创建适用于任何估算器的切换器类
from sklearn.base import BaseEstimator
class ClfSwitcher(BaseEstimator):
def __init__(
self,
estimator = SGDClassifier(),
):
"""
A Custom BaseEstimator that can switch between classifiers.
:param estimator: sklearn object - The classifier
"""
self.estimator = estimator
def fit(self, X, y=None, **kwargs):
self.estimator.fit(X, y)
return self
def predict(self, X, y=None):
return self.estimator.predict(X)
def predict_proba(self, X):
return self.estimator.predict_proba(X)
def score(self, X, y):
return self.estimator.score(X, y)
现在您可以为估计器参数传递任何内容。您可以优化传入的任何估计器的任何参数,如下所示:
执行超参数优化
from sklearn.feature_extraction.text import TfidfVectorizer
from sklearn.naive_bayes import MultinomialNB
from sklearn.linear_model import SGDClassifier
from sklearn.pipeline import Pipeline
from sklearn.model_selection import GridSearchCV
pipeline = Pipeline([
('tfidf', TfidfVectorizer()),
('clf', ClfSwitcher()),
])
parameters = [
{
'clf__estimator': [SGDClassifier()], # SVM if hinge loss / logreg if log loss
'tfidf__max_df': (0.25, 0.5, 0.75, 1.0),
'tfidf__stop_words': ['english', None],
'clf__estimator__penalty': ('l2', 'elasticnet', 'l1'),
'clf__estimator__max_iter': [50, 80],
'clf__estimator__tol': [1e-4],
'clf__estimator__loss': ['hinge', 'log', 'modified_huber'],
},
{
'clf__estimator': [MultinomialNB()],
'tfidf__max_df': (0.25, 0.5, 0.75, 1.0),
'tfidf__stop_words': [None],
'clf__estimator__alpha': (1e-2, 1e-3, 1e-1),
},
]
gscv = GridSearchCV(pipeline, parameters, cv=5, n_jobs=12, return_train_score=False, verbose=3)
gscv.fit(train_data, train_labels)
如何解读clf__estimator__loss
clf__estimator__loss
被解释为loss
任何参数estimator
在哪estimator = SGDClassifier()
在最上面的例子中,它本身就是一个参数clf
这是一个ClfSwitcher
object.