我想写一个Naive Base文本分类器。 因为sklearn不接受＆＃39;文本形式＆＃39;功能我正在使用TfidfVectorizer转换它们。
我成功地只使用转换后的数据作为特征来创建这样的分类。代码如下所示：
### text vectorization--go from strings to lists of numbers
vectorizer = TfidfVectorizer(sublinear_tf=True, max_df=0.5,
stop_words='english')
X_train_transformed = vectorizer.fit_transform(X_train_raw['url'])
X_test_transformed = vectorizer.transform(X_test_raw['url'])
### feature selection, because text is super high dimensional and
### can be really computationally chewy as a result
selector = SelectPercentile(f_classif, percentile=1)
selector.fit(X_train_transformed, y_train_raw)
X_train = selector.transform(X_train_transformed).toarray()
X_test = selector.transform(X_test_transformed).toarray()
clf = GaussianNB()
clf.fit(X_train, y_train_raw)
.....
一切都按预期工作，但当我想添加另一个功能时，我遇到了问题，例如。指示天气的标志给定文本包含特定关键字。 我尝试了多种方法来正确地改变“网址”。功能，然后将转换后的功能与另一个布尔功能相结合，但我没有成功。 假设我有一个包含两个特征的熊猫框架，应该如何做到这一点：＆＃39; url＆＃39; （我想转换）和＆＃39; contains_keyword＆＃39;旗？
失败的解决方案看起来像这样：
vectorizer = CountVectorizer(min_df=1)
X_train_transformed = vectorizer.fit_transform(X_train_raw['url'])
X_test_transformed = vectorizer.transform(X_test_raw['url'])
selector = SelectPercentile(f_classif, percentile=1)
selector.fit(X_train_transformed, y_train_raw)
X_train_selected = selector.transform(X_train_transformed)
X_test_selected = selector.transform(X_test_transformed)
X_train_raw['transformed_url'] = X_train_selected.toarray().tolist()
X_train_without = X_train_raw.drop(['url'], axis=1)
X_train = X_train_without.values
这会生成包含布尔标志的行和列表，这是sklearn模型的错误输入。我不知道我应该如何正确地改变它。感谢任何帮助。
以下是测试数据：
url,target,ads_keyword
googleadapis l google com,1,True
googleadapis l google com,1,True
clients1 google com,1,False
c go-mpulse net,1,False
translate google pl,1,False
url - 从dns查询中获取的分割域名
目标 - 分类的目标类
ads_keyword - 指示天气的标志“url＆＃39;包含＆＃39;广告＆＃39;字。
我想改变“网址”。使用TfidfVectorizer并将转换后的数据与＆＃39; ads_keyword＆＃39;一起使用（以及未来可能的更多功能）作为用于训练朴素贝叶斯模型的特征。
答案 0 :(得分：1)
这是一个演示，演示如何使用GridSearchCV联合功能以及如何调整超参数。
不幸的是，您的样本数据集太小而无法训练真实模型......
try:
from pathlib import Path
except ImportError: # Python 2
from pathlib2 import Path
import os
import re
from pprint import pprint
import pandas as pd
import numpy as np
from sklearn.base import BaseEstimator, TransformerMixin
from sklearn.preprocessing import FunctionTransformer, LabelEncoder, LabelBinarizer, StandardScaler
from sklearn.model_selection import train_test_split
from sklearn.feature_selection import SelectPercentile
from sklearn.feature_extraction import DictVectorizer
from sklearn.feature_extraction.text import CountVectorizer, TfidfVectorizer
from sklearn.model_selection import GridSearchCV
from sklearn.linear_model import SGDClassifier
from sklearn.naive_bayes import MultinomialNB, GaussianNB
from sklearn.neural_network import MLPClassifier
from sklearn.svm import SVC
from sklearn.pipeline import Pipeline, FeatureUnion
from sklearn.externals import joblib
from scipy.sparse import csr_matrix, hstack
class ColumnSelector(BaseEstimator, TransformerMixin):
def __init__(self, name=None, position=None,
as_cat_codes=False, sparse=False):
self.name = name
self.position = position
self.as_cat_codes = as_cat_codes
self.sparse = sparse
def fit(self, X, y=None):
return self
def transform(self, X, **kwargs):
if self.name is not None:
col_pos = X.columns.get_loc(self.name)
elif self.position is not None:
col_pos = self.position
else:
raise Exception('either [name] or [position] parameter must be not-None')
if self.as_cat_codes and X.dtypes.iloc[col_pos] == 'category':
ret = X.iloc[:, col_pos].cat.codes
else:
ret = X.iloc[:, col_pos]
if self.sparse:
ret = csr_matrix(ret.values.reshape(-1,1))
return ret
union = FeatureUnion([
('text',
Pipeline([
('select', ColumnSelector('url')),
#('pct', SelectPercentile(percentile=1)),
('vect', TfidfVectorizer(sublinear_tf=True, max_df=0.5,
stop_words='english')),
]) ),
('ads',
Pipeline([
('select', ColumnSelector('ads_keyword', sparse=True,
as_cat_codes=True)),
#('scale', StandardScaler(with_mean=False)),
]) )
])
pipe = Pipeline([
('union', union),
('clf', MultinomialNB())
])
param_grid = [
{
'union__text__vect': [TfidfVectorizer(sublinear_tf=True,
max_df=0.5,
stop_words='english')],
'clf': [SGDClassifier(max_iter=500)],
'union__text__vect__ngram_range': [(1,1), (2,5)],
'union__text__vect__analyzer': ['word','char_wb'],
'clf__alpha': np.logspace(-5, 0, 6),
#'clf__max_iter': [500],
},
{
'union__text__vect': [TfidfVectorizer(sublinear_tf=True,
max_df=0.5,
stop_words='english')],
'clf': [MultinomialNB()],
'union__text__vect__ngram_range': [(1,1), (2,5)],
'union__text__vect__analyzer': ['word','char_wb'],
'clf__alpha': np.logspace(-4, 2, 7),
},
#{ # NOTE: does NOT support sparse matrices!
# 'union__text__vect': [TfidfVectorizer(sublinear_tf=True,
# max_df=0.5,
# stop_words='english')],
# 'clf': [GaussianNB()],
# 'union__text__vect__ngram_range': [(1,1), (2,5)],
# 'union__text__vect__analyzer': ['word','char_wb'],
#},
]
gs_kwargs = dict(scoring='roc_auc', cv=3, n_jobs=1, verbose=2)
X_train, X_test, y_train, y_test = \
train_test_split(df[['url','ads_keyword']], df['target'], test_size=0.33)
grid = GridSearchCV(pipe, param_grid=param_grid, **gs_kwargs)
grid.fit(X_train, y_train)
# prediction
predicted = grid.predict(X_test)