python - 次线性 TF 变换导致 sklearn 中的 ValueError

Question

我正在做一些文档分类工作，我正在使用 sklearn 的散列向量化器，然后进行 tfidf 转换。如果 Tfidf 参数保持默认，我没有问题。但是，如果我设置 sublinear_tf=True，则会引发以下错误:

ValueError                                Traceback (most recent call last)
<ipython-input-16-137f187e99d8> in <module>()
----> 5 tfidf.transform(test)

D:\Users\DB\Anaconda\lib\site-packages\sklearn\feature_extraction\text.pyc in     transform(self, X, copy)
   1020 
   1021         if self.norm:
-> 1022             X = normalize(X, norm=self.norm, copy=False)
   1023 
   1024         return X

D:\Users\DB\Anaconda\lib\site-packages\sklearn\preprocessing\data.pyc in normalize(X, norm, axis, copy)
    533         raise ValueError("'%d' is not a supported axis" % axis)
    534 
--> 535     X = check_arrays(X, sparse_format=sparse_format, copy=copy)[0]
    536     warn_if_not_float(X, 'The normalize function')
    537     if axis == 0:

D:\Users\DB\Anaconda\lib\site-packages\sklearn\utils\validation.pyc in check_arrays(*arrays, **options)
    272                 if not allow_nans:
    273                     if hasattr(array, 'data'):
--> 274                         _assert_all_finite(array.data)
    275                     else:
    276                         _assert_all_finite(array.values())

D:\Users\DB\Anaconda\lib\site-packages\sklearn\utils\validation.pyc in _assert_all_finite(X)
     41             and not np.isfinite(X).all()):
     42         raise ValueError("Input contains NaN, infinity"
---> 43                          " or a value too large for %r." % X.dtype)
     44 
     45 

ValueError: Input contains NaN, infinity or a value too large for dtype('float64').

我找到了导致错误的最小文本样本并尝试了一些诊断:

hv_stops = HashingVectorizer(ngram_range=(1,2), preprocessor=neg_preprocess, stop_words='english')
tfidf = TfidfTransformer(sublinear_tf=True).fit(hv_stops.transform(X))
test = hv_stops.transform(X[4:6])
print np.any(np.isnan(test.todense())) #False
print np.any(np.isinf(test.todense())) #False
print np.all(np.isfinite(test.todense())) #True
tfidf.transform(test) #Raises the ValueError

对导致错误的原因有任何想法吗？如果需要更多信息，请告诉我。提前致谢!

编辑:

这个单一的文本项导致了我的错误:

hv_stops = HashingVectorizer(ngram_range=(1,3), stop_words='english', non_negative=True)
item = u'b number  b number  b number  conclusion  no product_neg was_neg returned_neg for_neg evaluation_neg  review of the medd history records did not find_neg any_neg deviations_neg or_neg anomalies_neg  it is not suspected_neg that_neg the_neg product_neg failed_neg to_neg meet_neg specifications_neg  the investigation could not verify_neg or_neg identify_neg any_neg evidence_neg of_neg a_neg medd_neg deficiency_neg causing_neg or_neg contributing_neg to_neg the_neg reported_neg problem_neg  based on the investigation  the need for corrective action is not indicated_neg  should additional information be received that changes this conclusion  an amended medd report will be filed  zimmer considers the investigation closed  this mdr is being submitted late  as this issue was identified during a retrospective review of complaint files '
li = [item]
fail = hv_stops.transform(li)
TfidfTransformer(sublinear_tf=True).fit_transform(fail)

Answer 1

我找到了原因。 TfidfTransformer 假定它获得的稀疏矩阵是规范的，即它在其 data 成员中不包含实际的零。但是，HashingVectorizer 生成一个包含存储零的稀疏矩阵。这会导致对数变换产生 -inf，而这又会导致归一化失败，因为矩阵具有无限范数。

这是 scikit-learn 中的一个错误；我做了一个report的，但我还不确定修复方法是什么。