如何添加另一个特征(文本长度)到当前的词袋分类?Scikit-learn

Question

我正在使用词袋对文本进行分类。它工作得很好，但我想知道如何添加一个功能，这不是一个词。

下面是我的示例代码。

import numpy as np
from sklearn.pipeline import Pipeline
from sklearn.feature_extraction.text import CountVectorizer
from sklearn.svm import LinearSVC
from sklearn.feature_extraction.text import TfidfTransformer
from sklearn.multiclass import OneVsRestClassifier
X_train = np.array(["new york is a hell of a town",
                    "new york was originally dutch",
                    "new york is also called the big apple",
                    "nyc is nice",
                    "the capital of great britain is london. london is a huge metropolis which has a great many number of people living in it. london is also a very old town with a rich and vibrant cultural history.",
                    "london is in the uk. they speak english there. london is a sprawling big city where it's super easy to get lost and i've got lost many times.",
                    "london is in england, which is a part of great britain. some cool things to check out in london are the museum and buckingham palace.",
                    "london is in great britain. it rains a lot in britain and london's fogs are a constant theme in books based in london, such as sherlock holmes. the weather is really bad there.",])
y_train = [[0],[0],[0],[0],[1],[1],[1],[1]]
X_test = np.array(["it's a nice day in nyc",
                   'i loved the time i spent in london, the weather was great, though there was a nip in the air and i had to wear a jacket.'
                   ])   
target_names = ['Class 1', 'Class 2']
classifier = Pipeline([
    ('vectorizer', CountVectorizer(min_df=1,max_df=2)),
    ('tfidf', TfidfTransformer()),
    ('clf', OneVsRestClassifier(LinearSVC()))])
classifier.fit(X_train, y_train)
predicted = classifier.predict(X_test)
for item, labels in zip(X_test, predicted):
    print '%s => %s' % (item, ', '.join(target_names[x] for x in labels))

现在很明显，关于伦敦的文章往往比关于纽约的文章长得多。我该如何添加文本长度作为功能?我是否需要使用另一种分类方法，然后将两种预测结合起来?有什么方法可以把它和这袋单词一起做吗?一些示例代码会很好——我是机器学习和scikit学习的新手。

Answer 1

如注释所示，这是一个FunctionTransformer, FeaturePipeline和FeatureUnion的组合。

import numpy as np
from sklearn.pipeline import Pipeline, FeatureUnion
from sklearn.feature_extraction.text import CountVectorizer
from sklearn.svm import LinearSVC
from sklearn.feature_extraction.text import TfidfTransformer
from sklearn.multiclass import OneVsRestClassifier
from sklearn.preprocessing import FunctionTransformer
X_train = np.array(["new york is a hell of a town",
                    "new york was originally dutch",
                    "new york is also called the big apple",
                    "nyc is nice",
                    "the capital of great britain is london. london is a huge metropolis which has a great many number of people living in it. london is also a very old town with a rich and vibrant cultural history.",
                    "london is in the uk. they speak english there. london is a sprawling big city where it's super easy to get lost and i've got lost many times.",
                    "london is in england, which is a part of great britain. some cool things to check out in london are the museum and buckingham palace.",
                    "london is in great britain. it rains a lot in britain and london's fogs are a constant theme in books based in london, such as sherlock holmes. the weather is really bad there.",])
y_train = np.array([[0],[0],[0],[0],[1],[1],[1],[1]])
X_test = np.array(["it's a nice day in nyc",
                   'i loved the time i spent in london, the weather was great, though there was a nip in the air and i had to wear a jacket.'
                   ])   
target_names = ['Class 1', 'Class 2']

def get_text_length(x):
    return np.array([len(t) for t in x]).reshape(-1, 1)
classifier = Pipeline([
    ('features', FeatureUnion([
        ('text', Pipeline([
            ('vectorizer', CountVectorizer(min_df=1,max_df=2)),
            ('tfidf', TfidfTransformer()),
        ])),
        ('length', Pipeline([
            ('count', FunctionTransformer(get_text_length, validate=False)),
        ]))
    ])),
    ('clf', OneVsRestClassifier(LinearSVC()))])
classifier.fit(X_train, y_train)
predicted = classifier.predict(X_test)
predicted

这将把文本的长度添加到分类器使用的特征中。

Answer 2

我假设您想要添加的新特性是数字。这是我的逻辑。首先使用TfidfTransformer或类似的东西将文本转换为稀疏。然后将稀疏表示转换为pandas DataFrame并添加我假设是数字的新列。最后，您可能希望使用scipy或任何其他您觉得舒服的模块将数据帧转换回sparse矩阵。我假设您的数据在pandas DataFrame中，称为dataset，包含'Text Column'和'Numeric Column'。下面是一些代码:

dataset = pd.DataFrame({'Text Column':['Sample Text1','Sample Text2'], 'Numeric Column': [2,1]})
dataset.head()
        Numeric Column   Text Column
0                   2    Sample Text1
1                   1    Sample Text2
from sklearn.feature_extraction.text import TfidfVectorizer, TfidfTransformer
from scipy import sparse
tv = TfidfVectorizer(min_df = 0.05, max_df = 0.5, stop_words = 'english')
X = tv.fit_transform(dataset['Text column'])
vocab = tv.get_feature_names()
X1 = pd.DataFrame(X.toarray(), columns = vocab)
X1['Numeric Column'] = dataset['Numeric Column']

X_sparse = sparse.csr_matrix(X1.values)

最后，您可能想要;

print(X_sparse.shape)
print(X.shape)

以确保新列已成功添加。