2167 lines
76 KiB
Python
2167 lines
76 KiB
Python
# Authors: Olivier Grisel <olivier.grisel@ensta.org>
|
|
# Mathieu Blondel <mathieu@mblondel.org>
|
|
# Lars Buitinck
|
|
# Robert Layton <robertlayton@gmail.com>
|
|
# Jochen Wersdörfer <jochen@wersdoerfer.de>
|
|
# Roman Sinayev <roman.sinayev@gmail.com>
|
|
#
|
|
# License: BSD 3 clause
|
|
"""
|
|
The :mod:`sklearn.feature_extraction.text` submodule gathers utilities to
|
|
build feature vectors from text documents.
|
|
"""
|
|
|
|
import array
|
|
import re
|
|
import unicodedata
|
|
import warnings
|
|
from collections import defaultdict
|
|
from collections.abc import Mapping
|
|
from functools import partial
|
|
from numbers import Integral
|
|
from operator import itemgetter
|
|
|
|
import numpy as np
|
|
import scipy.sparse as sp
|
|
|
|
from ..base import BaseEstimator, OneToOneFeatureMixin, TransformerMixin, _fit_context
|
|
from ..exceptions import NotFittedError
|
|
from ..preprocessing import normalize
|
|
from ..utils import _IS_32BIT
|
|
from ..utils._param_validation import HasMethods, Interval, RealNotInt, StrOptions
|
|
from ..utils.validation import FLOAT_DTYPES, check_array, check_is_fitted
|
|
from ._hash import FeatureHasher
|
|
from ._stop_words import ENGLISH_STOP_WORDS
|
|
|
|
__all__ = [
|
|
"HashingVectorizer",
|
|
"CountVectorizer",
|
|
"ENGLISH_STOP_WORDS",
|
|
"TfidfTransformer",
|
|
"TfidfVectorizer",
|
|
"strip_accents_ascii",
|
|
"strip_accents_unicode",
|
|
"strip_tags",
|
|
]
|
|
|
|
|
|
def _preprocess(doc, accent_function=None, lower=False):
|
|
"""Chain together an optional series of text preprocessing steps to
|
|
apply to a document.
|
|
|
|
Parameters
|
|
----------
|
|
doc: str
|
|
The string to preprocess
|
|
accent_function: callable, default=None
|
|
Function for handling accented characters. Common strategies include
|
|
normalizing and removing.
|
|
lower: bool, default=False
|
|
Whether to use str.lower to lowercase all of the text
|
|
|
|
Returns
|
|
-------
|
|
doc: str
|
|
preprocessed string
|
|
"""
|
|
if lower:
|
|
doc = doc.lower()
|
|
if accent_function is not None:
|
|
doc = accent_function(doc)
|
|
return doc
|
|
|
|
|
|
def _analyze(
|
|
doc,
|
|
analyzer=None,
|
|
tokenizer=None,
|
|
ngrams=None,
|
|
preprocessor=None,
|
|
decoder=None,
|
|
stop_words=None,
|
|
):
|
|
"""Chain together an optional series of text processing steps to go from
|
|
a single document to ngrams, with or without tokenizing or preprocessing.
|
|
|
|
If analyzer is used, only the decoder argument is used, as the analyzer is
|
|
intended to replace the preprocessor, tokenizer, and ngrams steps.
|
|
|
|
Parameters
|
|
----------
|
|
analyzer: callable, default=None
|
|
tokenizer: callable, default=None
|
|
ngrams: callable, default=None
|
|
preprocessor: callable, default=None
|
|
decoder: callable, default=None
|
|
stop_words: list, default=None
|
|
|
|
Returns
|
|
-------
|
|
ngrams: list
|
|
A sequence of tokens, possibly with pairs, triples, etc.
|
|
"""
|
|
|
|
if decoder is not None:
|
|
doc = decoder(doc)
|
|
if analyzer is not None:
|
|
doc = analyzer(doc)
|
|
else:
|
|
if preprocessor is not None:
|
|
doc = preprocessor(doc)
|
|
if tokenizer is not None:
|
|
doc = tokenizer(doc)
|
|
if ngrams is not None:
|
|
if stop_words is not None:
|
|
doc = ngrams(doc, stop_words)
|
|
else:
|
|
doc = ngrams(doc)
|
|
return doc
|
|
|
|
|
|
def strip_accents_unicode(s):
|
|
"""Transform accentuated unicode symbols into their simple counterpart.
|
|
|
|
Warning: the python-level loop and join operations make this
|
|
implementation 20 times slower than the strip_accents_ascii basic
|
|
normalization.
|
|
|
|
Parameters
|
|
----------
|
|
s : str
|
|
The string to strip.
|
|
|
|
Returns
|
|
-------
|
|
s : str
|
|
The stripped string.
|
|
|
|
See Also
|
|
--------
|
|
strip_accents_ascii : Remove accentuated char for any unicode symbol that
|
|
has a direct ASCII equivalent.
|
|
"""
|
|
try:
|
|
# If `s` is ASCII-compatible, then it does not contain any accented
|
|
# characters and we can avoid an expensive list comprehension
|
|
s.encode("ASCII", errors="strict")
|
|
return s
|
|
except UnicodeEncodeError:
|
|
normalized = unicodedata.normalize("NFKD", s)
|
|
return "".join([c for c in normalized if not unicodedata.combining(c)])
|
|
|
|
|
|
def strip_accents_ascii(s):
|
|
"""Transform accentuated unicode symbols into ascii or nothing.
|
|
|
|
Warning: this solution is only suited for languages that have a direct
|
|
transliteration to ASCII symbols.
|
|
|
|
Parameters
|
|
----------
|
|
s : str
|
|
The string to strip.
|
|
|
|
Returns
|
|
-------
|
|
s : str
|
|
The stripped string.
|
|
|
|
See Also
|
|
--------
|
|
strip_accents_unicode : Remove accentuated char for any unicode symbol.
|
|
"""
|
|
nkfd_form = unicodedata.normalize("NFKD", s)
|
|
return nkfd_form.encode("ASCII", "ignore").decode("ASCII")
|
|
|
|
|
|
def strip_tags(s):
|
|
"""Basic regexp based HTML / XML tag stripper function.
|
|
|
|
For serious HTML/XML preprocessing you should rather use an external
|
|
library such as lxml or BeautifulSoup.
|
|
|
|
Parameters
|
|
----------
|
|
s : str
|
|
The string to strip.
|
|
|
|
Returns
|
|
-------
|
|
s : str
|
|
The stripped string.
|
|
"""
|
|
return re.compile(r"<([^>]+)>", flags=re.UNICODE).sub(" ", s)
|
|
|
|
|
|
def _check_stop_list(stop):
|
|
if stop == "english":
|
|
return ENGLISH_STOP_WORDS
|
|
elif isinstance(stop, str):
|
|
raise ValueError("not a built-in stop list: %s" % stop)
|
|
elif stop is None:
|
|
return None
|
|
else: # assume it's a collection
|
|
return frozenset(stop)
|
|
|
|
|
|
class _VectorizerMixin:
|
|
"""Provides common code for text vectorizers (tokenization logic)."""
|
|
|
|
_white_spaces = re.compile(r"\s\s+")
|
|
|
|
def decode(self, doc):
|
|
"""Decode the input into a string of unicode symbols.
|
|
|
|
The decoding strategy depends on the vectorizer parameters.
|
|
|
|
Parameters
|
|
----------
|
|
doc : bytes or str
|
|
The string to decode.
|
|
|
|
Returns
|
|
-------
|
|
doc: str
|
|
A string of unicode symbols.
|
|
"""
|
|
if self.input == "filename":
|
|
with open(doc, "rb") as fh:
|
|
doc = fh.read()
|
|
|
|
elif self.input == "file":
|
|
doc = doc.read()
|
|
|
|
if isinstance(doc, bytes):
|
|
doc = doc.decode(self.encoding, self.decode_error)
|
|
|
|
if doc is np.nan:
|
|
raise ValueError(
|
|
"np.nan is an invalid document, expected byte or unicode string."
|
|
)
|
|
|
|
return doc
|
|
|
|
def _word_ngrams(self, tokens, stop_words=None):
|
|
"""Turn tokens into a sequence of n-grams after stop words filtering"""
|
|
# handle stop words
|
|
if stop_words is not None:
|
|
tokens = [w for w in tokens if w not in stop_words]
|
|
|
|
# handle token n-grams
|
|
min_n, max_n = self.ngram_range
|
|
if max_n != 1:
|
|
original_tokens = tokens
|
|
if min_n == 1:
|
|
# no need to do any slicing for unigrams
|
|
# just iterate through the original tokens
|
|
tokens = list(original_tokens)
|
|
min_n += 1
|
|
else:
|
|
tokens = []
|
|
|
|
n_original_tokens = len(original_tokens)
|
|
|
|
# bind method outside of loop to reduce overhead
|
|
tokens_append = tokens.append
|
|
space_join = " ".join
|
|
|
|
for n in range(min_n, min(max_n + 1, n_original_tokens + 1)):
|
|
for i in range(n_original_tokens - n + 1):
|
|
tokens_append(space_join(original_tokens[i : i + n]))
|
|
|
|
return tokens
|
|
|
|
def _char_ngrams(self, text_document):
|
|
"""Tokenize text_document into a sequence of character n-grams"""
|
|
# normalize white spaces
|
|
text_document = self._white_spaces.sub(" ", text_document)
|
|
|
|
text_len = len(text_document)
|
|
min_n, max_n = self.ngram_range
|
|
if min_n == 1:
|
|
# no need to do any slicing for unigrams
|
|
# iterate through the string
|
|
ngrams = list(text_document)
|
|
min_n += 1
|
|
else:
|
|
ngrams = []
|
|
|
|
# bind method outside of loop to reduce overhead
|
|
ngrams_append = ngrams.append
|
|
|
|
for n in range(min_n, min(max_n + 1, text_len + 1)):
|
|
for i in range(text_len - n + 1):
|
|
ngrams_append(text_document[i : i + n])
|
|
return ngrams
|
|
|
|
def _char_wb_ngrams(self, text_document):
|
|
"""Whitespace sensitive char-n-gram tokenization.
|
|
|
|
Tokenize text_document into a sequence of character n-grams
|
|
operating only inside word boundaries. n-grams at the edges
|
|
of words are padded with space."""
|
|
# normalize white spaces
|
|
text_document = self._white_spaces.sub(" ", text_document)
|
|
|
|
min_n, max_n = self.ngram_range
|
|
ngrams = []
|
|
|
|
# bind method outside of loop to reduce overhead
|
|
ngrams_append = ngrams.append
|
|
|
|
for w in text_document.split():
|
|
w = " " + w + " "
|
|
w_len = len(w)
|
|
for n in range(min_n, max_n + 1):
|
|
offset = 0
|
|
ngrams_append(w[offset : offset + n])
|
|
while offset + n < w_len:
|
|
offset += 1
|
|
ngrams_append(w[offset : offset + n])
|
|
if offset == 0: # count a short word (w_len < n) only once
|
|
break
|
|
return ngrams
|
|
|
|
def build_preprocessor(self):
|
|
"""Return a function to preprocess the text before tokenization.
|
|
|
|
Returns
|
|
-------
|
|
preprocessor: callable
|
|
A function to preprocess the text before tokenization.
|
|
"""
|
|
if self.preprocessor is not None:
|
|
return self.preprocessor
|
|
|
|
# accent stripping
|
|
if not self.strip_accents:
|
|
strip_accents = None
|
|
elif callable(self.strip_accents):
|
|
strip_accents = self.strip_accents
|
|
elif self.strip_accents == "ascii":
|
|
strip_accents = strip_accents_ascii
|
|
elif self.strip_accents == "unicode":
|
|
strip_accents = strip_accents_unicode
|
|
else:
|
|
raise ValueError(
|
|
'Invalid value for "strip_accents": %s' % self.strip_accents
|
|
)
|
|
|
|
return partial(_preprocess, accent_function=strip_accents, lower=self.lowercase)
|
|
|
|
def build_tokenizer(self):
|
|
"""Return a function that splits a string into a sequence of tokens.
|
|
|
|
Returns
|
|
-------
|
|
tokenizer: callable
|
|
A function to split a string into a sequence of tokens.
|
|
"""
|
|
if self.tokenizer is not None:
|
|
return self.tokenizer
|
|
token_pattern = re.compile(self.token_pattern)
|
|
|
|
if token_pattern.groups > 1:
|
|
raise ValueError(
|
|
"More than 1 capturing group in token pattern. Only a single "
|
|
"group should be captured."
|
|
)
|
|
|
|
return token_pattern.findall
|
|
|
|
def get_stop_words(self):
|
|
"""Build or fetch the effective stop words list.
|
|
|
|
Returns
|
|
-------
|
|
stop_words: list or None
|
|
A list of stop words.
|
|
"""
|
|
return _check_stop_list(self.stop_words)
|
|
|
|
def _check_stop_words_consistency(self, stop_words, preprocess, tokenize):
|
|
"""Check if stop words are consistent
|
|
|
|
Returns
|
|
-------
|
|
is_consistent : True if stop words are consistent with the preprocessor
|
|
and tokenizer, False if they are not, None if the check
|
|
was previously performed, "error" if it could not be
|
|
performed (e.g. because of the use of a custom
|
|
preprocessor / tokenizer)
|
|
"""
|
|
if id(self.stop_words) == getattr(self, "_stop_words_id", None):
|
|
# Stop words are were previously validated
|
|
return None
|
|
|
|
# NB: stop_words is validated, unlike self.stop_words
|
|
try:
|
|
inconsistent = set()
|
|
for w in stop_words or ():
|
|
tokens = list(tokenize(preprocess(w)))
|
|
for token in tokens:
|
|
if token not in stop_words:
|
|
inconsistent.add(token)
|
|
self._stop_words_id = id(self.stop_words)
|
|
|
|
if inconsistent:
|
|
warnings.warn(
|
|
"Your stop_words may be inconsistent with "
|
|
"your preprocessing. Tokenizing the stop "
|
|
"words generated tokens %r not in "
|
|
"stop_words."
|
|
% sorted(inconsistent)
|
|
)
|
|
return not inconsistent
|
|
except Exception:
|
|
# Failed to check stop words consistency (e.g. because a custom
|
|
# preprocessor or tokenizer was used)
|
|
self._stop_words_id = id(self.stop_words)
|
|
return "error"
|
|
|
|
def build_analyzer(self):
|
|
"""Return a callable to process input data.
|
|
|
|
The callable handles preprocessing, tokenization, and n-grams generation.
|
|
|
|
Returns
|
|
-------
|
|
analyzer: callable
|
|
A function to handle preprocessing, tokenization
|
|
and n-grams generation.
|
|
"""
|
|
|
|
if callable(self.analyzer):
|
|
return partial(_analyze, analyzer=self.analyzer, decoder=self.decode)
|
|
|
|
preprocess = self.build_preprocessor()
|
|
|
|
if self.analyzer == "char":
|
|
return partial(
|
|
_analyze,
|
|
ngrams=self._char_ngrams,
|
|
preprocessor=preprocess,
|
|
decoder=self.decode,
|
|
)
|
|
|
|
elif self.analyzer == "char_wb":
|
|
return partial(
|
|
_analyze,
|
|
ngrams=self._char_wb_ngrams,
|
|
preprocessor=preprocess,
|
|
decoder=self.decode,
|
|
)
|
|
|
|
elif self.analyzer == "word":
|
|
stop_words = self.get_stop_words()
|
|
tokenize = self.build_tokenizer()
|
|
self._check_stop_words_consistency(stop_words, preprocess, tokenize)
|
|
return partial(
|
|
_analyze,
|
|
ngrams=self._word_ngrams,
|
|
tokenizer=tokenize,
|
|
preprocessor=preprocess,
|
|
decoder=self.decode,
|
|
stop_words=stop_words,
|
|
)
|
|
|
|
else:
|
|
raise ValueError(
|
|
"%s is not a valid tokenization scheme/analyzer" % self.analyzer
|
|
)
|
|
|
|
def _validate_vocabulary(self):
|
|
vocabulary = self.vocabulary
|
|
if vocabulary is not None:
|
|
if isinstance(vocabulary, set):
|
|
vocabulary = sorted(vocabulary)
|
|
if not isinstance(vocabulary, Mapping):
|
|
vocab = {}
|
|
for i, t in enumerate(vocabulary):
|
|
if vocab.setdefault(t, i) != i:
|
|
msg = "Duplicate term in vocabulary: %r" % t
|
|
raise ValueError(msg)
|
|
vocabulary = vocab
|
|
else:
|
|
indices = set(vocabulary.values())
|
|
if len(indices) != len(vocabulary):
|
|
raise ValueError("Vocabulary contains repeated indices.")
|
|
for i in range(len(vocabulary)):
|
|
if i not in indices:
|
|
msg = "Vocabulary of size %d doesn't contain index %d." % (
|
|
len(vocabulary),
|
|
i,
|
|
)
|
|
raise ValueError(msg)
|
|
if not vocabulary:
|
|
raise ValueError("empty vocabulary passed to fit")
|
|
self.fixed_vocabulary_ = True
|
|
self.vocabulary_ = dict(vocabulary)
|
|
else:
|
|
self.fixed_vocabulary_ = False
|
|
|
|
def _check_vocabulary(self):
|
|
"""Check if vocabulary is empty or missing (not fitted)"""
|
|
if not hasattr(self, "vocabulary_"):
|
|
self._validate_vocabulary()
|
|
if not self.fixed_vocabulary_:
|
|
raise NotFittedError("Vocabulary not fitted or provided")
|
|
|
|
if len(self.vocabulary_) == 0:
|
|
raise ValueError("Vocabulary is empty")
|
|
|
|
def _validate_ngram_range(self):
|
|
"""Check validity of ngram_range parameter"""
|
|
min_n, max_m = self.ngram_range
|
|
if min_n > max_m:
|
|
raise ValueError(
|
|
"Invalid value for ngram_range=%s "
|
|
"lower boundary larger than the upper boundary."
|
|
% str(self.ngram_range)
|
|
)
|
|
|
|
def _warn_for_unused_params(self):
|
|
if self.tokenizer is not None and self.token_pattern is not None:
|
|
warnings.warn(
|
|
"The parameter 'token_pattern' will not be used"
|
|
" since 'tokenizer' is not None'"
|
|
)
|
|
|
|
if self.preprocessor is not None and callable(self.analyzer):
|
|
warnings.warn(
|
|
"The parameter 'preprocessor' will not be used"
|
|
" since 'analyzer' is callable'"
|
|
)
|
|
|
|
if (
|
|
self.ngram_range != (1, 1)
|
|
and self.ngram_range is not None
|
|
and callable(self.analyzer)
|
|
):
|
|
warnings.warn(
|
|
"The parameter 'ngram_range' will not be used"
|
|
" since 'analyzer' is callable'"
|
|
)
|
|
if self.analyzer != "word" or callable(self.analyzer):
|
|
if self.stop_words is not None:
|
|
warnings.warn(
|
|
"The parameter 'stop_words' will not be used"
|
|
" since 'analyzer' != 'word'"
|
|
)
|
|
if (
|
|
self.token_pattern is not None
|
|
and self.token_pattern != r"(?u)\b\w\w+\b"
|
|
):
|
|
warnings.warn(
|
|
"The parameter 'token_pattern' will not be used"
|
|
" since 'analyzer' != 'word'"
|
|
)
|
|
if self.tokenizer is not None:
|
|
warnings.warn(
|
|
"The parameter 'tokenizer' will not be used"
|
|
" since 'analyzer' != 'word'"
|
|
)
|
|
|
|
|
|
class HashingVectorizer(
|
|
TransformerMixin, _VectorizerMixin, BaseEstimator, auto_wrap_output_keys=None
|
|
):
|
|
r"""Convert a collection of text documents to a matrix of token occurrences.
|
|
|
|
It turns a collection of text documents into a scipy.sparse matrix holding
|
|
token occurrence counts (or binary occurrence information), possibly
|
|
normalized as token frequencies if norm='l1' or projected on the euclidean
|
|
unit sphere if norm='l2'.
|
|
|
|
This text vectorizer implementation uses the hashing trick to find the
|
|
token string name to feature integer index mapping.
|
|
|
|
This strategy has several advantages:
|
|
|
|
- it is very low memory scalable to large datasets as there is no need to
|
|
store a vocabulary dictionary in memory.
|
|
|
|
- it is fast to pickle and un-pickle as it holds no state besides the
|
|
constructor parameters.
|
|
|
|
- it can be used in a streaming (partial fit) or parallel pipeline as there
|
|
is no state computed during fit.
|
|
|
|
There are also a couple of cons (vs using a CountVectorizer with an
|
|
in-memory vocabulary):
|
|
|
|
- there is no way to compute the inverse transform (from feature indices to
|
|
string feature names) which can be a problem when trying to introspect
|
|
which features are most important to a model.
|
|
|
|
- there can be collisions: distinct tokens can be mapped to the same
|
|
feature index. However in practice this is rarely an issue if n_features
|
|
is large enough (e.g. 2 ** 18 for text classification problems).
|
|
|
|
- no IDF weighting as this would render the transformer stateful.
|
|
|
|
The hash function employed is the signed 32-bit version of Murmurhash3.
|
|
|
|
For an efficiency comparison of the different feature extractors, see
|
|
:ref:`sphx_glr_auto_examples_text_plot_hashing_vs_dict_vectorizer.py`.
|
|
|
|
Read more in the :ref:`User Guide <text_feature_extraction>`.
|
|
|
|
Parameters
|
|
----------
|
|
input : {'filename', 'file', 'content'}, default='content'
|
|
- If `'filename'`, the sequence passed as an argument to fit is
|
|
expected to be a list of filenames that need reading to fetch
|
|
the raw content to analyze.
|
|
|
|
- If `'file'`, the sequence items must have a 'read' method (file-like
|
|
object) that is called to fetch the bytes in memory.
|
|
|
|
- If `'content'`, the input is expected to be a sequence of items that
|
|
can be of type string or byte.
|
|
|
|
encoding : str, default='utf-8'
|
|
If bytes or files are given to analyze, this encoding is used to
|
|
decode.
|
|
|
|
decode_error : {'strict', 'ignore', 'replace'}, default='strict'
|
|
Instruction on what to do if a byte sequence is given to analyze that
|
|
contains characters not of the given `encoding`. By default, it is
|
|
'strict', meaning that a UnicodeDecodeError will be raised. Other
|
|
values are 'ignore' and 'replace'.
|
|
|
|
strip_accents : {'ascii', 'unicode'} or callable, default=None
|
|
Remove accents and perform other character normalization
|
|
during the preprocessing step.
|
|
'ascii' is a fast method that only works on characters that have
|
|
a direct ASCII mapping.
|
|
'unicode' is a slightly slower method that works on any character.
|
|
None (default) means no character normalization is performed.
|
|
|
|
Both 'ascii' and 'unicode' use NFKD normalization from
|
|
:func:`unicodedata.normalize`.
|
|
|
|
lowercase : bool, default=True
|
|
Convert all characters to lowercase before tokenizing.
|
|
|
|
preprocessor : callable, default=None
|
|
Override the preprocessing (string transformation) stage while
|
|
preserving the tokenizing and n-grams generation steps.
|
|
Only applies if ``analyzer`` is not callable.
|
|
|
|
tokenizer : callable, default=None
|
|
Override the string tokenization step while preserving the
|
|
preprocessing and n-grams generation steps.
|
|
Only applies if ``analyzer == 'word'``.
|
|
|
|
stop_words : {'english'}, list, default=None
|
|
If 'english', a built-in stop word list for English is used.
|
|
There are several known issues with 'english' and you should
|
|
consider an alternative (see :ref:`stop_words`).
|
|
|
|
If a list, that list is assumed to contain stop words, all of which
|
|
will be removed from the resulting tokens.
|
|
Only applies if ``analyzer == 'word'``.
|
|
|
|
token_pattern : str or None, default=r"(?u)\\b\\w\\w+\\b"
|
|
Regular expression denoting what constitutes a "token", only used
|
|
if ``analyzer == 'word'``. The default regexp selects tokens of 2
|
|
or more alphanumeric characters (punctuation is completely ignored
|
|
and always treated as a token separator).
|
|
|
|
If there is a capturing group in token_pattern then the
|
|
captured group content, not the entire match, becomes the token.
|
|
At most one capturing group is permitted.
|
|
|
|
ngram_range : tuple (min_n, max_n), default=(1, 1)
|
|
The lower and upper boundary of the range of n-values for different
|
|
n-grams to be extracted. All values of n such that min_n <= n <= max_n
|
|
will be used. For example an ``ngram_range`` of ``(1, 1)`` means only
|
|
unigrams, ``(1, 2)`` means unigrams and bigrams, and ``(2, 2)`` means
|
|
only bigrams.
|
|
Only applies if ``analyzer`` is not callable.
|
|
|
|
analyzer : {'word', 'char', 'char_wb'} or callable, default='word'
|
|
Whether the feature should be made of word or character n-grams.
|
|
Option 'char_wb' creates character n-grams only from text inside
|
|
word boundaries; n-grams at the edges of words are padded with space.
|
|
|
|
If a callable is passed it is used to extract the sequence of features
|
|
out of the raw, unprocessed input.
|
|
|
|
.. versionchanged:: 0.21
|
|
Since v0.21, if ``input`` is ``'filename'`` or ``'file'``, the data
|
|
is first read from the file and then passed to the given callable
|
|
analyzer.
|
|
|
|
n_features : int, default=(2 ** 20)
|
|
The number of features (columns) in the output matrices. Small numbers
|
|
of features are likely to cause hash collisions, but large numbers
|
|
will cause larger coefficient dimensions in linear learners.
|
|
|
|
binary : bool, default=False
|
|
If True, all non zero counts are set to 1. This is useful for discrete
|
|
probabilistic models that model binary events rather than integer
|
|
counts.
|
|
|
|
norm : {'l1', 'l2'}, default='l2'
|
|
Norm used to normalize term vectors. None for no normalization.
|
|
|
|
alternate_sign : bool, default=True
|
|
When True, an alternating sign is added to the features as to
|
|
approximately conserve the inner product in the hashed space even for
|
|
small n_features. This approach is similar to sparse random projection.
|
|
|
|
.. versionadded:: 0.19
|
|
|
|
dtype : type, default=np.float64
|
|
Type of the matrix returned by fit_transform() or transform().
|
|
|
|
See Also
|
|
--------
|
|
CountVectorizer : Convert a collection of text documents to a matrix of
|
|
token counts.
|
|
TfidfVectorizer : Convert a collection of raw documents to a matrix of
|
|
TF-IDF features.
|
|
|
|
Notes
|
|
-----
|
|
This estimator is :term:`stateless` and does not need to be fitted.
|
|
However, we recommend to call :meth:`fit_transform` instead of
|
|
:meth:`transform`, as parameter validation is only performed in
|
|
:meth:`fit`.
|
|
|
|
Examples
|
|
--------
|
|
>>> from sklearn.feature_extraction.text import HashingVectorizer
|
|
>>> corpus = [
|
|
... 'This is the first document.',
|
|
... 'This document is the second document.',
|
|
... 'And this is the third one.',
|
|
... 'Is this the first document?',
|
|
... ]
|
|
>>> vectorizer = HashingVectorizer(n_features=2**4)
|
|
>>> X = vectorizer.fit_transform(corpus)
|
|
>>> print(X.shape)
|
|
(4, 16)
|
|
"""
|
|
|
|
_parameter_constraints: dict = {
|
|
"input": [StrOptions({"filename", "file", "content"})],
|
|
"encoding": [str],
|
|
"decode_error": [StrOptions({"strict", "ignore", "replace"})],
|
|
"strip_accents": [StrOptions({"ascii", "unicode"}), None, callable],
|
|
"lowercase": ["boolean"],
|
|
"preprocessor": [callable, None],
|
|
"tokenizer": [callable, None],
|
|
"stop_words": [StrOptions({"english"}), list, None],
|
|
"token_pattern": [str, None],
|
|
"ngram_range": [tuple],
|
|
"analyzer": [StrOptions({"word", "char", "char_wb"}), callable],
|
|
"n_features": [Interval(Integral, 1, np.iinfo(np.int32).max, closed="left")],
|
|
"binary": ["boolean"],
|
|
"norm": [StrOptions({"l1", "l2"}), None],
|
|
"alternate_sign": ["boolean"],
|
|
"dtype": "no_validation", # delegate to numpy
|
|
}
|
|
|
|
def __init__(
|
|
self,
|
|
*,
|
|
input="content",
|
|
encoding="utf-8",
|
|
decode_error="strict",
|
|
strip_accents=None,
|
|
lowercase=True,
|
|
preprocessor=None,
|
|
tokenizer=None,
|
|
stop_words=None,
|
|
token_pattern=r"(?u)\b\w\w+\b",
|
|
ngram_range=(1, 1),
|
|
analyzer="word",
|
|
n_features=(2**20),
|
|
binary=False,
|
|
norm="l2",
|
|
alternate_sign=True,
|
|
dtype=np.float64,
|
|
):
|
|
self.input = input
|
|
self.encoding = encoding
|
|
self.decode_error = decode_error
|
|
self.strip_accents = strip_accents
|
|
self.preprocessor = preprocessor
|
|
self.tokenizer = tokenizer
|
|
self.analyzer = analyzer
|
|
self.lowercase = lowercase
|
|
self.token_pattern = token_pattern
|
|
self.stop_words = stop_words
|
|
self.n_features = n_features
|
|
self.ngram_range = ngram_range
|
|
self.binary = binary
|
|
self.norm = norm
|
|
self.alternate_sign = alternate_sign
|
|
self.dtype = dtype
|
|
|
|
@_fit_context(prefer_skip_nested_validation=True)
|
|
def partial_fit(self, X, y=None):
|
|
"""Only validates estimator's parameters.
|
|
|
|
This method allows to: (i) validate the estimator's parameters and
|
|
(ii) be consistent with the scikit-learn transformer API.
|
|
|
|
Parameters
|
|
----------
|
|
X : ndarray of shape [n_samples, n_features]
|
|
Training data.
|
|
|
|
y : Ignored
|
|
Not used, present for API consistency by convention.
|
|
|
|
Returns
|
|
-------
|
|
self : object
|
|
HashingVectorizer instance.
|
|
"""
|
|
return self
|
|
|
|
@_fit_context(prefer_skip_nested_validation=True)
|
|
def fit(self, X, y=None):
|
|
"""Only validates estimator's parameters.
|
|
|
|
This method allows to: (i) validate the estimator's parameters and
|
|
(ii) be consistent with the scikit-learn transformer API.
|
|
|
|
Parameters
|
|
----------
|
|
X : ndarray of shape [n_samples, n_features]
|
|
Training data.
|
|
|
|
y : Ignored
|
|
Not used, present for API consistency by convention.
|
|
|
|
Returns
|
|
-------
|
|
self : object
|
|
HashingVectorizer instance.
|
|
"""
|
|
# triggers a parameter validation
|
|
if isinstance(X, str):
|
|
raise ValueError(
|
|
"Iterable over raw text documents expected, string object received."
|
|
)
|
|
|
|
self._warn_for_unused_params()
|
|
self._validate_ngram_range()
|
|
|
|
self._get_hasher().fit(X, y=y)
|
|
return self
|
|
|
|
def transform(self, X):
|
|
"""Transform a sequence of documents to a document-term matrix.
|
|
|
|
Parameters
|
|
----------
|
|
X : iterable over raw text documents, length = n_samples
|
|
Samples. Each sample must be a text document (either bytes or
|
|
unicode strings, file name or file object depending on the
|
|
constructor argument) which will be tokenized and hashed.
|
|
|
|
Returns
|
|
-------
|
|
X : sparse matrix of shape (n_samples, n_features)
|
|
Document-term matrix.
|
|
"""
|
|
if isinstance(X, str):
|
|
raise ValueError(
|
|
"Iterable over raw text documents expected, string object received."
|
|
)
|
|
|
|
self._validate_ngram_range()
|
|
|
|
analyzer = self.build_analyzer()
|
|
X = self._get_hasher().transform(analyzer(doc) for doc in X)
|
|
if self.binary:
|
|
X.data.fill(1)
|
|
if self.norm is not None:
|
|
X = normalize(X, norm=self.norm, copy=False)
|
|
return X
|
|
|
|
def fit_transform(self, X, y=None):
|
|
"""Transform a sequence of documents to a document-term matrix.
|
|
|
|
Parameters
|
|
----------
|
|
X : iterable over raw text documents, length = n_samples
|
|
Samples. Each sample must be a text document (either bytes or
|
|
unicode strings, file name or file object depending on the
|
|
constructor argument) which will be tokenized and hashed.
|
|
y : any
|
|
Ignored. This parameter exists only for compatibility with
|
|
sklearn.pipeline.Pipeline.
|
|
|
|
Returns
|
|
-------
|
|
X : sparse matrix of shape (n_samples, n_features)
|
|
Document-term matrix.
|
|
"""
|
|
return self.fit(X, y).transform(X)
|
|
|
|
def _get_hasher(self):
|
|
return FeatureHasher(
|
|
n_features=self.n_features,
|
|
input_type="string",
|
|
dtype=self.dtype,
|
|
alternate_sign=self.alternate_sign,
|
|
)
|
|
|
|
def _more_tags(self):
|
|
return {"X_types": ["string"]}
|
|
|
|
|
|
def _document_frequency(X):
|
|
"""Count the number of non-zero values for each feature in sparse X."""
|
|
if sp.issparse(X) and X.format == "csr":
|
|
return np.bincount(X.indices, minlength=X.shape[1])
|
|
else:
|
|
return np.diff(X.indptr)
|
|
|
|
|
|
class CountVectorizer(_VectorizerMixin, BaseEstimator):
|
|
r"""Convert a collection of text documents to a matrix of token counts.
|
|
|
|
This implementation produces a sparse representation of the counts using
|
|
scipy.sparse.csr_matrix.
|
|
|
|
If you do not provide an a-priori dictionary and you do not use an analyzer
|
|
that does some kind of feature selection then the number of features will
|
|
be equal to the vocabulary size found by analyzing the data.
|
|
|
|
For an efficiency comparison of the different feature extractors, see
|
|
:ref:`sphx_glr_auto_examples_text_plot_hashing_vs_dict_vectorizer.py`.
|
|
|
|
Read more in the :ref:`User Guide <text_feature_extraction>`.
|
|
|
|
Parameters
|
|
----------
|
|
input : {'filename', 'file', 'content'}, default='content'
|
|
- If `'filename'`, the sequence passed as an argument to fit is
|
|
expected to be a list of filenames that need reading to fetch
|
|
the raw content to analyze.
|
|
|
|
- If `'file'`, the sequence items must have a 'read' method (file-like
|
|
object) that is called to fetch the bytes in memory.
|
|
|
|
- If `'content'`, the input is expected to be a sequence of items that
|
|
can be of type string or byte.
|
|
|
|
encoding : str, default='utf-8'
|
|
If bytes or files are given to analyze, this encoding is used to
|
|
decode.
|
|
|
|
decode_error : {'strict', 'ignore', 'replace'}, default='strict'
|
|
Instruction on what to do if a byte sequence is given to analyze that
|
|
contains characters not of the given `encoding`. By default, it is
|
|
'strict', meaning that a UnicodeDecodeError will be raised. Other
|
|
values are 'ignore' and 'replace'.
|
|
|
|
strip_accents : {'ascii', 'unicode'} or callable, default=None
|
|
Remove accents and perform other character normalization
|
|
during the preprocessing step.
|
|
'ascii' is a fast method that only works on characters that have
|
|
a direct ASCII mapping.
|
|
'unicode' is a slightly slower method that works on any characters.
|
|
None (default) means no character normalization is performed.
|
|
|
|
Both 'ascii' and 'unicode' use NFKD normalization from
|
|
:func:`unicodedata.normalize`.
|
|
|
|
lowercase : bool, default=True
|
|
Convert all characters to lowercase before tokenizing.
|
|
|
|
preprocessor : callable, default=None
|
|
Override the preprocessing (strip_accents and lowercase) stage while
|
|
preserving the tokenizing and n-grams generation steps.
|
|
Only applies if ``analyzer`` is not callable.
|
|
|
|
tokenizer : callable, default=None
|
|
Override the string tokenization step while preserving the
|
|
preprocessing and n-grams generation steps.
|
|
Only applies if ``analyzer == 'word'``.
|
|
|
|
stop_words : {'english'}, list, default=None
|
|
If 'english', a built-in stop word list for English is used.
|
|
There are several known issues with 'english' and you should
|
|
consider an alternative (see :ref:`stop_words`).
|
|
|
|
If a list, that list is assumed to contain stop words, all of which
|
|
will be removed from the resulting tokens.
|
|
Only applies if ``analyzer == 'word'``.
|
|
|
|
If None, no stop words will be used. In this case, setting `max_df`
|
|
to a higher value, such as in the range (0.7, 1.0), can automatically detect
|
|
and filter stop words based on intra corpus document frequency of terms.
|
|
|
|
token_pattern : str or None, default=r"(?u)\\b\\w\\w+\\b"
|
|
Regular expression denoting what constitutes a "token", only used
|
|
if ``analyzer == 'word'``. The default regexp select tokens of 2
|
|
or more alphanumeric characters (punctuation is completely ignored
|
|
and always treated as a token separator).
|
|
|
|
If there is a capturing group in token_pattern then the
|
|
captured group content, not the entire match, becomes the token.
|
|
At most one capturing group is permitted.
|
|
|
|
ngram_range : tuple (min_n, max_n), default=(1, 1)
|
|
The lower and upper boundary of the range of n-values for different
|
|
word n-grams or char n-grams to be extracted. All values of n such
|
|
such that min_n <= n <= max_n will be used. For example an
|
|
``ngram_range`` of ``(1, 1)`` means only unigrams, ``(1, 2)`` means
|
|
unigrams and bigrams, and ``(2, 2)`` means only bigrams.
|
|
Only applies if ``analyzer`` is not callable.
|
|
|
|
analyzer : {'word', 'char', 'char_wb'} or callable, default='word'
|
|
Whether the feature should be made of word n-gram or character
|
|
n-grams.
|
|
Option 'char_wb' creates character n-grams only from text inside
|
|
word boundaries; n-grams at the edges of words are padded with space.
|
|
|
|
If a callable is passed it is used to extract the sequence of features
|
|
out of the raw, unprocessed input.
|
|
|
|
.. versionchanged:: 0.21
|
|
|
|
Since v0.21, if ``input`` is ``filename`` or ``file``, the data is
|
|
first read from the file and then passed to the given callable
|
|
analyzer.
|
|
|
|
max_df : float in range [0.0, 1.0] or int, default=1.0
|
|
When building the vocabulary ignore terms that have a document
|
|
frequency strictly higher than the given threshold (corpus-specific
|
|
stop words).
|
|
If float, the parameter represents a proportion of documents, integer
|
|
absolute counts.
|
|
This parameter is ignored if vocabulary is not None.
|
|
|
|
min_df : float in range [0.0, 1.0] or int, default=1
|
|
When building the vocabulary ignore terms that have a document
|
|
frequency strictly lower than the given threshold. This value is also
|
|
called cut-off in the literature.
|
|
If float, the parameter represents a proportion of documents, integer
|
|
absolute counts.
|
|
This parameter is ignored if vocabulary is not None.
|
|
|
|
max_features : int, default=None
|
|
If not None, build a vocabulary that only consider the top
|
|
`max_features` ordered by term frequency across the corpus.
|
|
Otherwise, all features are used.
|
|
|
|
This parameter is ignored if vocabulary is not None.
|
|
|
|
vocabulary : Mapping or iterable, default=None
|
|
Either a Mapping (e.g., a dict) where keys are terms and values are
|
|
indices in the feature matrix, or an iterable over terms. If not
|
|
given, a vocabulary is determined from the input documents. Indices
|
|
in the mapping should not be repeated and should not have any gap
|
|
between 0 and the largest index.
|
|
|
|
binary : bool, default=False
|
|
If True, all non zero counts are set to 1. This is useful for discrete
|
|
probabilistic models that model binary events rather than integer
|
|
counts.
|
|
|
|
dtype : dtype, default=np.int64
|
|
Type of the matrix returned by fit_transform() or transform().
|
|
|
|
Attributes
|
|
----------
|
|
vocabulary_ : dict
|
|
A mapping of terms to feature indices.
|
|
|
|
fixed_vocabulary_ : bool
|
|
True if a fixed vocabulary of term to indices mapping
|
|
is provided by the user.
|
|
|
|
stop_words_ : set
|
|
Terms that were ignored because they either:
|
|
|
|
- occurred in too many documents (`max_df`)
|
|
- occurred in too few documents (`min_df`)
|
|
- were cut off by feature selection (`max_features`).
|
|
|
|
This is only available if no vocabulary was given.
|
|
|
|
See Also
|
|
--------
|
|
HashingVectorizer : Convert a collection of text documents to a
|
|
matrix of token counts.
|
|
|
|
TfidfVectorizer : Convert a collection of raw documents to a matrix
|
|
of TF-IDF features.
|
|
|
|
Notes
|
|
-----
|
|
The ``stop_words_`` attribute can get large and increase the model size
|
|
when pickling. This attribute is provided only for introspection and can
|
|
be safely removed using delattr or set to None before pickling.
|
|
|
|
Examples
|
|
--------
|
|
>>> from sklearn.feature_extraction.text import CountVectorizer
|
|
>>> corpus = [
|
|
... 'This is the first document.',
|
|
... 'This document is the second document.',
|
|
... 'And this is the third one.',
|
|
... 'Is this the first document?',
|
|
... ]
|
|
>>> vectorizer = CountVectorizer()
|
|
>>> X = vectorizer.fit_transform(corpus)
|
|
>>> vectorizer.get_feature_names_out()
|
|
array(['and', 'document', 'first', 'is', 'one', 'second', 'the', 'third',
|
|
'this'], ...)
|
|
>>> print(X.toarray())
|
|
[[0 1 1 1 0 0 1 0 1]
|
|
[0 2 0 1 0 1 1 0 1]
|
|
[1 0 0 1 1 0 1 1 1]
|
|
[0 1 1 1 0 0 1 0 1]]
|
|
>>> vectorizer2 = CountVectorizer(analyzer='word', ngram_range=(2, 2))
|
|
>>> X2 = vectorizer2.fit_transform(corpus)
|
|
>>> vectorizer2.get_feature_names_out()
|
|
array(['and this', 'document is', 'first document', 'is the', 'is this',
|
|
'second document', 'the first', 'the second', 'the third', 'third one',
|
|
'this document', 'this is', 'this the'], ...)
|
|
>>> print(X2.toarray())
|
|
[[0 0 1 1 0 0 1 0 0 0 0 1 0]
|
|
[0 1 0 1 0 1 0 1 0 0 1 0 0]
|
|
[1 0 0 1 0 0 0 0 1 1 0 1 0]
|
|
[0 0 1 0 1 0 1 0 0 0 0 0 1]]
|
|
"""
|
|
|
|
_parameter_constraints: dict = {
|
|
"input": [StrOptions({"filename", "file", "content"})],
|
|
"encoding": [str],
|
|
"decode_error": [StrOptions({"strict", "ignore", "replace"})],
|
|
"strip_accents": [StrOptions({"ascii", "unicode"}), None, callable],
|
|
"lowercase": ["boolean"],
|
|
"preprocessor": [callable, None],
|
|
"tokenizer": [callable, None],
|
|
"stop_words": [StrOptions({"english"}), list, None],
|
|
"token_pattern": [str, None],
|
|
"ngram_range": [tuple],
|
|
"analyzer": [StrOptions({"word", "char", "char_wb"}), callable],
|
|
"max_df": [
|
|
Interval(RealNotInt, 0, 1, closed="both"),
|
|
Interval(Integral, 1, None, closed="left"),
|
|
],
|
|
"min_df": [
|
|
Interval(RealNotInt, 0, 1, closed="both"),
|
|
Interval(Integral, 1, None, closed="left"),
|
|
],
|
|
"max_features": [Interval(Integral, 1, None, closed="left"), None],
|
|
"vocabulary": [Mapping, HasMethods("__iter__"), None],
|
|
"binary": ["boolean"],
|
|
"dtype": "no_validation", # delegate to numpy
|
|
}
|
|
|
|
def __init__(
|
|
self,
|
|
*,
|
|
input="content",
|
|
encoding="utf-8",
|
|
decode_error="strict",
|
|
strip_accents=None,
|
|
lowercase=True,
|
|
preprocessor=None,
|
|
tokenizer=None,
|
|
stop_words=None,
|
|
token_pattern=r"(?u)\b\w\w+\b",
|
|
ngram_range=(1, 1),
|
|
analyzer="word",
|
|
max_df=1.0,
|
|
min_df=1,
|
|
max_features=None,
|
|
vocabulary=None,
|
|
binary=False,
|
|
dtype=np.int64,
|
|
):
|
|
self.input = input
|
|
self.encoding = encoding
|
|
self.decode_error = decode_error
|
|
self.strip_accents = strip_accents
|
|
self.preprocessor = preprocessor
|
|
self.tokenizer = tokenizer
|
|
self.analyzer = analyzer
|
|
self.lowercase = lowercase
|
|
self.token_pattern = token_pattern
|
|
self.stop_words = stop_words
|
|
self.max_df = max_df
|
|
self.min_df = min_df
|
|
self.max_features = max_features
|
|
self.ngram_range = ngram_range
|
|
self.vocabulary = vocabulary
|
|
self.binary = binary
|
|
self.dtype = dtype
|
|
|
|
def _sort_features(self, X, vocabulary):
|
|
"""Sort features by name
|
|
|
|
Returns a reordered matrix and modifies the vocabulary in place
|
|
"""
|
|
sorted_features = sorted(vocabulary.items())
|
|
map_index = np.empty(len(sorted_features), dtype=X.indices.dtype)
|
|
for new_val, (term, old_val) in enumerate(sorted_features):
|
|
vocabulary[term] = new_val
|
|
map_index[old_val] = new_val
|
|
|
|
X.indices = map_index.take(X.indices, mode="clip")
|
|
return X
|
|
|
|
def _limit_features(self, X, vocabulary, high=None, low=None, limit=None):
|
|
"""Remove too rare or too common features.
|
|
|
|
Prune features that are non zero in more samples than high or less
|
|
documents than low, modifying the vocabulary, and restricting it to
|
|
at most the limit most frequent.
|
|
|
|
This does not prune samples with zero features.
|
|
"""
|
|
if high is None and low is None and limit is None:
|
|
return X, set()
|
|
|
|
# Calculate a mask based on document frequencies
|
|
dfs = _document_frequency(X)
|
|
mask = np.ones(len(dfs), dtype=bool)
|
|
if high is not None:
|
|
mask &= dfs <= high
|
|
if low is not None:
|
|
mask &= dfs >= low
|
|
if limit is not None and mask.sum() > limit:
|
|
tfs = np.asarray(X.sum(axis=0)).ravel()
|
|
mask_inds = (-tfs[mask]).argsort()[:limit]
|
|
new_mask = np.zeros(len(dfs), dtype=bool)
|
|
new_mask[np.where(mask)[0][mask_inds]] = True
|
|
mask = new_mask
|
|
|
|
new_indices = np.cumsum(mask) - 1 # maps old indices to new
|
|
removed_terms = set()
|
|
for term, old_index in list(vocabulary.items()):
|
|
if mask[old_index]:
|
|
vocabulary[term] = new_indices[old_index]
|
|
else:
|
|
del vocabulary[term]
|
|
removed_terms.add(term)
|
|
kept_indices = np.where(mask)[0]
|
|
if len(kept_indices) == 0:
|
|
raise ValueError(
|
|
"After pruning, no terms remain. Try a lower min_df or a higher max_df."
|
|
)
|
|
return X[:, kept_indices], removed_terms
|
|
|
|
def _count_vocab(self, raw_documents, fixed_vocab):
|
|
"""Create sparse feature matrix, and vocabulary where fixed_vocab=False"""
|
|
if fixed_vocab:
|
|
vocabulary = self.vocabulary_
|
|
else:
|
|
# Add a new value when a new vocabulary item is seen
|
|
vocabulary = defaultdict()
|
|
vocabulary.default_factory = vocabulary.__len__
|
|
|
|
analyze = self.build_analyzer()
|
|
j_indices = []
|
|
indptr = []
|
|
|
|
values = _make_int_array()
|
|
indptr.append(0)
|
|
for doc in raw_documents:
|
|
feature_counter = {}
|
|
for feature in analyze(doc):
|
|
try:
|
|
feature_idx = vocabulary[feature]
|
|
if feature_idx not in feature_counter:
|
|
feature_counter[feature_idx] = 1
|
|
else:
|
|
feature_counter[feature_idx] += 1
|
|
except KeyError:
|
|
# Ignore out-of-vocabulary items for fixed_vocab=True
|
|
continue
|
|
|
|
j_indices.extend(feature_counter.keys())
|
|
values.extend(feature_counter.values())
|
|
indptr.append(len(j_indices))
|
|
|
|
if not fixed_vocab:
|
|
# disable defaultdict behaviour
|
|
vocabulary = dict(vocabulary)
|
|
if not vocabulary:
|
|
raise ValueError(
|
|
"empty vocabulary; perhaps the documents only contain stop words"
|
|
)
|
|
|
|
if indptr[-1] > np.iinfo(np.int32).max: # = 2**31 - 1
|
|
if _IS_32BIT:
|
|
raise ValueError(
|
|
(
|
|
"sparse CSR array has {} non-zero "
|
|
"elements and requires 64 bit indexing, "
|
|
"which is unsupported with 32 bit Python."
|
|
).format(indptr[-1])
|
|
)
|
|
indices_dtype = np.int64
|
|
|
|
else:
|
|
indices_dtype = np.int32
|
|
j_indices = np.asarray(j_indices, dtype=indices_dtype)
|
|
indptr = np.asarray(indptr, dtype=indices_dtype)
|
|
values = np.frombuffer(values, dtype=np.intc)
|
|
|
|
X = sp.csr_matrix(
|
|
(values, j_indices, indptr),
|
|
shape=(len(indptr) - 1, len(vocabulary)),
|
|
dtype=self.dtype,
|
|
)
|
|
X.sort_indices()
|
|
return vocabulary, X
|
|
|
|
def fit(self, raw_documents, y=None):
|
|
"""Learn a vocabulary dictionary of all tokens in the raw documents.
|
|
|
|
Parameters
|
|
----------
|
|
raw_documents : iterable
|
|
An iterable which generates either str, unicode or file objects.
|
|
|
|
y : None
|
|
This parameter is ignored.
|
|
|
|
Returns
|
|
-------
|
|
self : object
|
|
Fitted vectorizer.
|
|
"""
|
|
self.fit_transform(raw_documents)
|
|
return self
|
|
|
|
@_fit_context(prefer_skip_nested_validation=True)
|
|
def fit_transform(self, raw_documents, y=None):
|
|
"""Learn the vocabulary dictionary and return document-term matrix.
|
|
|
|
This is equivalent to fit followed by transform, but more efficiently
|
|
implemented.
|
|
|
|
Parameters
|
|
----------
|
|
raw_documents : iterable
|
|
An iterable which generates either str, unicode or file objects.
|
|
|
|
y : None
|
|
This parameter is ignored.
|
|
|
|
Returns
|
|
-------
|
|
X : array of shape (n_samples, n_features)
|
|
Document-term matrix.
|
|
"""
|
|
# We intentionally don't call the transform method to make
|
|
# fit_transform overridable without unwanted side effects in
|
|
# TfidfVectorizer.
|
|
if isinstance(raw_documents, str):
|
|
raise ValueError(
|
|
"Iterable over raw text documents expected, string object received."
|
|
)
|
|
|
|
self._validate_ngram_range()
|
|
self._warn_for_unused_params()
|
|
self._validate_vocabulary()
|
|
max_df = self.max_df
|
|
min_df = self.min_df
|
|
max_features = self.max_features
|
|
|
|
if self.fixed_vocabulary_ and self.lowercase:
|
|
for term in self.vocabulary:
|
|
if any(map(str.isupper, term)):
|
|
warnings.warn(
|
|
"Upper case characters found in"
|
|
" vocabulary while 'lowercase'"
|
|
" is True. These entries will not"
|
|
" be matched with any documents"
|
|
)
|
|
break
|
|
|
|
vocabulary, X = self._count_vocab(raw_documents, self.fixed_vocabulary_)
|
|
|
|
if self.binary:
|
|
X.data.fill(1)
|
|
|
|
if not self.fixed_vocabulary_:
|
|
n_doc = X.shape[0]
|
|
max_doc_count = max_df if isinstance(max_df, Integral) else max_df * n_doc
|
|
min_doc_count = min_df if isinstance(min_df, Integral) else min_df * n_doc
|
|
if max_doc_count < min_doc_count:
|
|
raise ValueError("max_df corresponds to < documents than min_df")
|
|
if max_features is not None:
|
|
X = self._sort_features(X, vocabulary)
|
|
X, self.stop_words_ = self._limit_features(
|
|
X, vocabulary, max_doc_count, min_doc_count, max_features
|
|
)
|
|
if max_features is None:
|
|
X = self._sort_features(X, vocabulary)
|
|
self.vocabulary_ = vocabulary
|
|
|
|
return X
|
|
|
|
def transform(self, raw_documents):
|
|
"""Transform documents to document-term matrix.
|
|
|
|
Extract token counts out of raw text documents using the vocabulary
|
|
fitted with fit or the one provided to the constructor.
|
|
|
|
Parameters
|
|
----------
|
|
raw_documents : iterable
|
|
An iterable which generates either str, unicode or file objects.
|
|
|
|
Returns
|
|
-------
|
|
X : sparse matrix of shape (n_samples, n_features)
|
|
Document-term matrix.
|
|
"""
|
|
if isinstance(raw_documents, str):
|
|
raise ValueError(
|
|
"Iterable over raw text documents expected, string object received."
|
|
)
|
|
self._check_vocabulary()
|
|
|
|
# use the same matrix-building strategy as fit_transform
|
|
_, X = self._count_vocab(raw_documents, fixed_vocab=True)
|
|
if self.binary:
|
|
X.data.fill(1)
|
|
return X
|
|
|
|
def inverse_transform(self, X):
|
|
"""Return terms per document with nonzero entries in X.
|
|
|
|
Parameters
|
|
----------
|
|
X : {array-like, sparse matrix} of shape (n_samples, n_features)
|
|
Document-term matrix.
|
|
|
|
Returns
|
|
-------
|
|
X_inv : list of arrays of shape (n_samples,)
|
|
List of arrays of terms.
|
|
"""
|
|
self._check_vocabulary()
|
|
# We need CSR format for fast row manipulations.
|
|
X = check_array(X, accept_sparse="csr")
|
|
n_samples = X.shape[0]
|
|
|
|
terms = np.array(list(self.vocabulary_.keys()))
|
|
indices = np.array(list(self.vocabulary_.values()))
|
|
inverse_vocabulary = terms[np.argsort(indices)]
|
|
|
|
if sp.issparse(X):
|
|
return [
|
|
inverse_vocabulary[X[i, :].nonzero()[1]].ravel()
|
|
for i in range(n_samples)
|
|
]
|
|
else:
|
|
return [
|
|
inverse_vocabulary[np.flatnonzero(X[i, :])].ravel()
|
|
for i in range(n_samples)
|
|
]
|
|
|
|
def get_feature_names_out(self, input_features=None):
|
|
"""Get output feature names for transformation.
|
|
|
|
Parameters
|
|
----------
|
|
input_features : array-like of str or None, default=None
|
|
Not used, present here for API consistency by convention.
|
|
|
|
Returns
|
|
-------
|
|
feature_names_out : ndarray of str objects
|
|
Transformed feature names.
|
|
"""
|
|
self._check_vocabulary()
|
|
return np.asarray(
|
|
[t for t, i in sorted(self.vocabulary_.items(), key=itemgetter(1))],
|
|
dtype=object,
|
|
)
|
|
|
|
def _more_tags(self):
|
|
return {"X_types": ["string"]}
|
|
|
|
|
|
def _make_int_array():
|
|
"""Construct an array.array of a type suitable for scipy.sparse indices."""
|
|
return array.array(str("i"))
|
|
|
|
|
|
class TfidfTransformer(
|
|
OneToOneFeatureMixin, TransformerMixin, BaseEstimator, auto_wrap_output_keys=None
|
|
):
|
|
"""Transform a count matrix to a normalized tf or tf-idf representation.
|
|
|
|
Tf means term-frequency while tf-idf means term-frequency times inverse
|
|
document-frequency. This is a common term weighting scheme in information
|
|
retrieval, that has also found good use in document classification.
|
|
|
|
The goal of using tf-idf instead of the raw frequencies of occurrence of a
|
|
token in a given document is to scale down the impact of tokens that occur
|
|
very frequently in a given corpus and that are hence empirically less
|
|
informative than features that occur in a small fraction of the training
|
|
corpus.
|
|
|
|
The formula that is used to compute the tf-idf for a term t of a document d
|
|
in a document set is tf-idf(t, d) = tf(t, d) * idf(t), and the idf is
|
|
computed as idf(t) = log [ n / df(t) ] + 1 (if ``smooth_idf=False``), where
|
|
n is the total number of documents in the document set and df(t) is the
|
|
document frequency of t; the document frequency is the number of documents
|
|
in the document set that contain the term t. The effect of adding "1" to
|
|
the idf in the equation above is that terms with zero idf, i.e., terms
|
|
that occur in all documents in a training set, will not be entirely
|
|
ignored.
|
|
(Note that the idf formula above differs from the standard textbook
|
|
notation that defines the idf as
|
|
idf(t) = log [ n / (df(t) + 1) ]).
|
|
|
|
If ``smooth_idf=True`` (the default), the constant "1" is added to the
|
|
numerator and denominator of the idf as if an extra document was seen
|
|
containing every term in the collection exactly once, which prevents
|
|
zero divisions: idf(t) = log [ (1 + n) / (1 + df(t)) ] + 1.
|
|
|
|
Furthermore, the formulas used to compute tf and idf depend
|
|
on parameter settings that correspond to the SMART notation used in IR
|
|
as follows:
|
|
|
|
Tf is "n" (natural) by default, "l" (logarithmic) when
|
|
``sublinear_tf=True``.
|
|
Idf is "t" when use_idf is given, "n" (none) otherwise.
|
|
Normalization is "c" (cosine) when ``norm='l2'``, "n" (none)
|
|
when ``norm=None``.
|
|
|
|
Read more in the :ref:`User Guide <text_feature_extraction>`.
|
|
|
|
Parameters
|
|
----------
|
|
norm : {'l1', 'l2'} or None, default='l2'
|
|
Each output row will have unit norm, either:
|
|
|
|
- 'l2': Sum of squares of vector elements is 1. The cosine
|
|
similarity between two vectors is their dot product when l2 norm has
|
|
been applied.
|
|
- 'l1': Sum of absolute values of vector elements is 1.
|
|
See :func:`~sklearn.preprocessing.normalize`.
|
|
- None: No normalization.
|
|
|
|
use_idf : bool, default=True
|
|
Enable inverse-document-frequency reweighting. If False, idf(t) = 1.
|
|
|
|
smooth_idf : bool, default=True
|
|
Smooth idf weights by adding one to document frequencies, as if an
|
|
extra document was seen containing every term in the collection
|
|
exactly once. Prevents zero divisions.
|
|
|
|
sublinear_tf : bool, default=False
|
|
Apply sublinear tf scaling, i.e. replace tf with 1 + log(tf).
|
|
|
|
Attributes
|
|
----------
|
|
idf_ : array of shape (n_features)
|
|
The inverse document frequency (IDF) vector; only defined
|
|
if ``use_idf`` is True.
|
|
|
|
.. versionadded:: 0.20
|
|
|
|
n_features_in_ : int
|
|
Number of features seen during :term:`fit`.
|
|
|
|
.. versionadded:: 1.0
|
|
|
|
feature_names_in_ : ndarray of shape (`n_features_in_`,)
|
|
Names of features seen during :term:`fit`. Defined only when `X`
|
|
has feature names that are all strings.
|
|
|
|
.. versionadded:: 1.0
|
|
|
|
See Also
|
|
--------
|
|
CountVectorizer : Transforms text into a sparse matrix of n-gram counts.
|
|
|
|
TfidfVectorizer : Convert a collection of raw documents to a matrix of
|
|
TF-IDF features.
|
|
|
|
HashingVectorizer : Convert a collection of text documents to a matrix
|
|
of token occurrences.
|
|
|
|
References
|
|
----------
|
|
.. [Yates2011] R. Baeza-Yates and B. Ribeiro-Neto (2011). Modern
|
|
Information Retrieval. Addison Wesley, pp. 68-74.
|
|
|
|
.. [MRS2008] C.D. Manning, P. Raghavan and H. Schütze (2008).
|
|
Introduction to Information Retrieval. Cambridge University
|
|
Press, pp. 118-120.
|
|
|
|
Examples
|
|
--------
|
|
>>> from sklearn.feature_extraction.text import TfidfTransformer
|
|
>>> from sklearn.feature_extraction.text import CountVectorizer
|
|
>>> from sklearn.pipeline import Pipeline
|
|
>>> corpus = ['this is the first document',
|
|
... 'this document is the second document',
|
|
... 'and this is the third one',
|
|
... 'is this the first document']
|
|
>>> vocabulary = ['this', 'document', 'first', 'is', 'second', 'the',
|
|
... 'and', 'one']
|
|
>>> pipe = Pipeline([('count', CountVectorizer(vocabulary=vocabulary)),
|
|
... ('tfid', TfidfTransformer())]).fit(corpus)
|
|
>>> pipe['count'].transform(corpus).toarray()
|
|
array([[1, 1, 1, 1, 0, 1, 0, 0],
|
|
[1, 2, 0, 1, 1, 1, 0, 0],
|
|
[1, 0, 0, 1, 0, 1, 1, 1],
|
|
[1, 1, 1, 1, 0, 1, 0, 0]])
|
|
>>> pipe['tfid'].idf_
|
|
array([1. , 1.22314355, 1.51082562, 1. , 1.91629073,
|
|
1. , 1.91629073, 1.91629073])
|
|
>>> pipe.transform(corpus).shape
|
|
(4, 8)
|
|
"""
|
|
|
|
_parameter_constraints: dict = {
|
|
"norm": [StrOptions({"l1", "l2"}), None],
|
|
"use_idf": ["boolean"],
|
|
"smooth_idf": ["boolean"],
|
|
"sublinear_tf": ["boolean"],
|
|
}
|
|
|
|
def __init__(self, *, norm="l2", use_idf=True, smooth_idf=True, sublinear_tf=False):
|
|
self.norm = norm
|
|
self.use_idf = use_idf
|
|
self.smooth_idf = smooth_idf
|
|
self.sublinear_tf = sublinear_tf
|
|
|
|
@_fit_context(prefer_skip_nested_validation=True)
|
|
def fit(self, X, y=None):
|
|
"""Learn the idf vector (global term weights).
|
|
|
|
Parameters
|
|
----------
|
|
X : sparse matrix of shape (n_samples, n_features)
|
|
A matrix of term/token counts.
|
|
|
|
y : None
|
|
This parameter is not needed to compute tf-idf.
|
|
|
|
Returns
|
|
-------
|
|
self : object
|
|
Fitted transformer.
|
|
"""
|
|
# large sparse data is not supported for 32bit platforms because
|
|
# _document_frequency uses np.bincount which works on arrays of
|
|
# dtype NPY_INTP which is int32 for 32bit platforms. See #20923
|
|
X = self._validate_data(
|
|
X, accept_sparse=("csr", "csc"), accept_large_sparse=not _IS_32BIT
|
|
)
|
|
if not sp.issparse(X):
|
|
X = sp.csr_matrix(X)
|
|
dtype = X.dtype if X.dtype in FLOAT_DTYPES else np.float64
|
|
|
|
if self.use_idf:
|
|
n_samples, n_features = X.shape
|
|
df = _document_frequency(X)
|
|
df = df.astype(dtype, copy=False)
|
|
|
|
# perform idf smoothing if required
|
|
df += int(self.smooth_idf)
|
|
n_samples += int(self.smooth_idf)
|
|
|
|
# log+1 instead of log makes sure terms with zero idf don't get
|
|
# suppressed entirely.
|
|
idf = np.log(n_samples / df) + 1
|
|
self._idf_diag = sp.diags(
|
|
idf,
|
|
offsets=0,
|
|
shape=(n_features, n_features),
|
|
format="csr",
|
|
dtype=dtype,
|
|
)
|
|
|
|
return self
|
|
|
|
def transform(self, X, copy=True):
|
|
"""Transform a count matrix to a tf or tf-idf representation.
|
|
|
|
Parameters
|
|
----------
|
|
X : sparse matrix of (n_samples, n_features)
|
|
A matrix of term/token counts.
|
|
|
|
copy : bool, default=True
|
|
Whether to copy X and operate on the copy or perform in-place
|
|
operations.
|
|
|
|
Returns
|
|
-------
|
|
vectors : sparse matrix of shape (n_samples, n_features)
|
|
Tf-idf-weighted document-term matrix.
|
|
"""
|
|
X = self._validate_data(
|
|
X, accept_sparse="csr", dtype=FLOAT_DTYPES, copy=copy, reset=False
|
|
)
|
|
if not sp.issparse(X):
|
|
X = sp.csr_matrix(X, dtype=np.float64)
|
|
|
|
if self.sublinear_tf:
|
|
np.log(X.data, X.data)
|
|
X.data += 1
|
|
|
|
if self.use_idf:
|
|
# idf_ being a property, the automatic attributes detection
|
|
# does not work as usual and we need to specify the attribute
|
|
# name:
|
|
check_is_fitted(self, attributes=["idf_"], msg="idf vector is not fitted")
|
|
|
|
X = X @ self._idf_diag
|
|
|
|
if self.norm is not None:
|
|
X = normalize(X, norm=self.norm, copy=False)
|
|
|
|
return X
|
|
|
|
@property
|
|
def idf_(self):
|
|
"""Inverse document frequency vector, only defined if `use_idf=True`.
|
|
|
|
Returns
|
|
-------
|
|
ndarray of shape (n_features,)
|
|
"""
|
|
# if _idf_diag is not set, this will raise an attribute error,
|
|
# which means hasattr(self, "idf_") is False
|
|
return np.ravel(self._idf_diag.sum(axis=0))
|
|
|
|
@idf_.setter
|
|
def idf_(self, value):
|
|
value = np.asarray(value, dtype=np.float64)
|
|
n_features = value.shape[0]
|
|
self._idf_diag = sp.spdiags(
|
|
value, diags=0, m=n_features, n=n_features, format="csr"
|
|
)
|
|
|
|
def _more_tags(self):
|
|
return {"X_types": ["2darray", "sparse"]}
|
|
|
|
|
|
class TfidfVectorizer(CountVectorizer):
|
|
r"""Convert a collection of raw documents to a matrix of TF-IDF features.
|
|
|
|
Equivalent to :class:`CountVectorizer` followed by
|
|
:class:`TfidfTransformer`.
|
|
|
|
For an example of usage, see
|
|
:ref:`sphx_glr_auto_examples_text_plot_document_classification_20newsgroups.py`.
|
|
|
|
For an efficiency comparison of the different feature extractors, see
|
|
:ref:`sphx_glr_auto_examples_text_plot_hashing_vs_dict_vectorizer.py`.
|
|
|
|
Read more in the :ref:`User Guide <text_feature_extraction>`.
|
|
|
|
Parameters
|
|
----------
|
|
input : {'filename', 'file', 'content'}, default='content'
|
|
- If `'filename'`, the sequence passed as an argument to fit is
|
|
expected to be a list of filenames that need reading to fetch
|
|
the raw content to analyze.
|
|
|
|
- If `'file'`, the sequence items must have a 'read' method (file-like
|
|
object) that is called to fetch the bytes in memory.
|
|
|
|
- If `'content'`, the input is expected to be a sequence of items that
|
|
can be of type string or byte.
|
|
|
|
encoding : str, default='utf-8'
|
|
If bytes or files are given to analyze, this encoding is used to
|
|
decode.
|
|
|
|
decode_error : {'strict', 'ignore', 'replace'}, default='strict'
|
|
Instruction on what to do if a byte sequence is given to analyze that
|
|
contains characters not of the given `encoding`. By default, it is
|
|
'strict', meaning that a UnicodeDecodeError will be raised. Other
|
|
values are 'ignore' and 'replace'.
|
|
|
|
strip_accents : {'ascii', 'unicode'} or callable, default=None
|
|
Remove accents and perform other character normalization
|
|
during the preprocessing step.
|
|
'ascii' is a fast method that only works on characters that have
|
|
a direct ASCII mapping.
|
|
'unicode' is a slightly slower method that works on any characters.
|
|
None (default) means no character normalization is performed.
|
|
|
|
Both 'ascii' and 'unicode' use NFKD normalization from
|
|
:func:`unicodedata.normalize`.
|
|
|
|
lowercase : bool, default=True
|
|
Convert all characters to lowercase before tokenizing.
|
|
|
|
preprocessor : callable, default=None
|
|
Override the preprocessing (string transformation) stage while
|
|
preserving the tokenizing and n-grams generation steps.
|
|
Only applies if ``analyzer`` is not callable.
|
|
|
|
tokenizer : callable, default=None
|
|
Override the string tokenization step while preserving the
|
|
preprocessing and n-grams generation steps.
|
|
Only applies if ``analyzer == 'word'``.
|
|
|
|
analyzer : {'word', 'char', 'char_wb'} or callable, default='word'
|
|
Whether the feature should be made of word or character n-grams.
|
|
Option 'char_wb' creates character n-grams only from text inside
|
|
word boundaries; n-grams at the edges of words are padded with space.
|
|
|
|
If a callable is passed it is used to extract the sequence of features
|
|
out of the raw, unprocessed input.
|
|
|
|
.. versionchanged:: 0.21
|
|
Since v0.21, if ``input`` is ``'filename'`` or ``'file'``, the data
|
|
is first read from the file and then passed to the given callable
|
|
analyzer.
|
|
|
|
stop_words : {'english'}, list, default=None
|
|
If a string, it is passed to _check_stop_list and the appropriate stop
|
|
list is returned. 'english' is currently the only supported string
|
|
value.
|
|
There are several known issues with 'english' and you should
|
|
consider an alternative (see :ref:`stop_words`).
|
|
|
|
If a list, that list is assumed to contain stop words, all of which
|
|
will be removed from the resulting tokens.
|
|
Only applies if ``analyzer == 'word'``.
|
|
|
|
If None, no stop words will be used. In this case, setting `max_df`
|
|
to a higher value, such as in the range (0.7, 1.0), can automatically detect
|
|
and filter stop words based on intra corpus document frequency of terms.
|
|
|
|
token_pattern : str, default=r"(?u)\\b\\w\\w+\\b"
|
|
Regular expression denoting what constitutes a "token", only used
|
|
if ``analyzer == 'word'``. The default regexp selects tokens of 2
|
|
or more alphanumeric characters (punctuation is completely ignored
|
|
and always treated as a token separator).
|
|
|
|
If there is a capturing group in token_pattern then the
|
|
captured group content, not the entire match, becomes the token.
|
|
At most one capturing group is permitted.
|
|
|
|
ngram_range : tuple (min_n, max_n), default=(1, 1)
|
|
The lower and upper boundary of the range of n-values for different
|
|
n-grams to be extracted. All values of n such that min_n <= n <= max_n
|
|
will be used. For example an ``ngram_range`` of ``(1, 1)`` means only
|
|
unigrams, ``(1, 2)`` means unigrams and bigrams, and ``(2, 2)`` means
|
|
only bigrams.
|
|
Only applies if ``analyzer`` is not callable.
|
|
|
|
max_df : float or int, default=1.0
|
|
When building the vocabulary ignore terms that have a document
|
|
frequency strictly higher than the given threshold (corpus-specific
|
|
stop words).
|
|
If float in range [0.0, 1.0], the parameter represents a proportion of
|
|
documents, integer absolute counts.
|
|
This parameter is ignored if vocabulary is not None.
|
|
|
|
min_df : float or int, default=1
|
|
When building the vocabulary ignore terms that have a document
|
|
frequency strictly lower than the given threshold. This value is also
|
|
called cut-off in the literature.
|
|
If float in range of [0.0, 1.0], the parameter represents a proportion
|
|
of documents, integer absolute counts.
|
|
This parameter is ignored if vocabulary is not None.
|
|
|
|
max_features : int, default=None
|
|
If not None, build a vocabulary that only consider the top
|
|
`max_features` ordered by term frequency across the corpus.
|
|
Otherwise, all features are used.
|
|
|
|
This parameter is ignored if vocabulary is not None.
|
|
|
|
vocabulary : Mapping or iterable, default=None
|
|
Either a Mapping (e.g., a dict) where keys are terms and values are
|
|
indices in the feature matrix, or an iterable over terms. If not
|
|
given, a vocabulary is determined from the input documents.
|
|
|
|
binary : bool, default=False
|
|
If True, all non-zero term counts are set to 1. This does not mean
|
|
outputs will have only 0/1 values, only that the tf term in tf-idf
|
|
is binary. (Set `binary` to True, `use_idf` to False and
|
|
`norm` to None to get 0/1 outputs).
|
|
|
|
dtype : dtype, default=float64
|
|
Type of the matrix returned by fit_transform() or transform().
|
|
|
|
norm : {'l1', 'l2'} or None, default='l2'
|
|
Each output row will have unit norm, either:
|
|
|
|
- 'l2': Sum of squares of vector elements is 1. The cosine
|
|
similarity between two vectors is their dot product when l2 norm has
|
|
been applied.
|
|
- 'l1': Sum of absolute values of vector elements is 1.
|
|
See :func:`~sklearn.preprocessing.normalize`.
|
|
- None: No normalization.
|
|
|
|
use_idf : bool, default=True
|
|
Enable inverse-document-frequency reweighting. If False, idf(t) = 1.
|
|
|
|
smooth_idf : bool, default=True
|
|
Smooth idf weights by adding one to document frequencies, as if an
|
|
extra document was seen containing every term in the collection
|
|
exactly once. Prevents zero divisions.
|
|
|
|
sublinear_tf : bool, default=False
|
|
Apply sublinear tf scaling, i.e. replace tf with 1 + log(tf).
|
|
|
|
Attributes
|
|
----------
|
|
vocabulary_ : dict
|
|
A mapping of terms to feature indices.
|
|
|
|
fixed_vocabulary_ : bool
|
|
True if a fixed vocabulary of term to indices mapping
|
|
is provided by the user.
|
|
|
|
idf_ : array of shape (n_features,)
|
|
The inverse document frequency (IDF) vector; only defined
|
|
if ``use_idf`` is True.
|
|
|
|
stop_words_ : set
|
|
Terms that were ignored because they either:
|
|
|
|
- occurred in too many documents (`max_df`)
|
|
- occurred in too few documents (`min_df`)
|
|
- were cut off by feature selection (`max_features`).
|
|
|
|
This is only available if no vocabulary was given.
|
|
|
|
See Also
|
|
--------
|
|
CountVectorizer : Transforms text into a sparse matrix of n-gram counts.
|
|
|
|
TfidfTransformer : Performs the TF-IDF transformation from a provided
|
|
matrix of counts.
|
|
|
|
Notes
|
|
-----
|
|
The ``stop_words_`` attribute can get large and increase the model size
|
|
when pickling. This attribute is provided only for introspection and can
|
|
be safely removed using delattr or set to None before pickling.
|
|
|
|
Examples
|
|
--------
|
|
>>> from sklearn.feature_extraction.text import TfidfVectorizer
|
|
>>> corpus = [
|
|
... 'This is the first document.',
|
|
... 'This document is the second document.',
|
|
... 'And this is the third one.',
|
|
... 'Is this the first document?',
|
|
... ]
|
|
>>> vectorizer = TfidfVectorizer()
|
|
>>> X = vectorizer.fit_transform(corpus)
|
|
>>> vectorizer.get_feature_names_out()
|
|
array(['and', 'document', 'first', 'is', 'one', 'second', 'the', 'third',
|
|
'this'], ...)
|
|
>>> print(X.shape)
|
|
(4, 9)
|
|
"""
|
|
|
|
_parameter_constraints: dict = {**CountVectorizer._parameter_constraints}
|
|
_parameter_constraints.update(
|
|
{
|
|
"norm": [StrOptions({"l1", "l2"}), None],
|
|
"use_idf": ["boolean"],
|
|
"smooth_idf": ["boolean"],
|
|
"sublinear_tf": ["boolean"],
|
|
}
|
|
)
|
|
|
|
def __init__(
|
|
self,
|
|
*,
|
|
input="content",
|
|
encoding="utf-8",
|
|
decode_error="strict",
|
|
strip_accents=None,
|
|
lowercase=True,
|
|
preprocessor=None,
|
|
tokenizer=None,
|
|
analyzer="word",
|
|
stop_words=None,
|
|
token_pattern=r"(?u)\b\w\w+\b",
|
|
ngram_range=(1, 1),
|
|
max_df=1.0,
|
|
min_df=1,
|
|
max_features=None,
|
|
vocabulary=None,
|
|
binary=False,
|
|
dtype=np.float64,
|
|
norm="l2",
|
|
use_idf=True,
|
|
smooth_idf=True,
|
|
sublinear_tf=False,
|
|
):
|
|
super().__init__(
|
|
input=input,
|
|
encoding=encoding,
|
|
decode_error=decode_error,
|
|
strip_accents=strip_accents,
|
|
lowercase=lowercase,
|
|
preprocessor=preprocessor,
|
|
tokenizer=tokenizer,
|
|
analyzer=analyzer,
|
|
stop_words=stop_words,
|
|
token_pattern=token_pattern,
|
|
ngram_range=ngram_range,
|
|
max_df=max_df,
|
|
min_df=min_df,
|
|
max_features=max_features,
|
|
vocabulary=vocabulary,
|
|
binary=binary,
|
|
dtype=dtype,
|
|
)
|
|
self.norm = norm
|
|
self.use_idf = use_idf
|
|
self.smooth_idf = smooth_idf
|
|
self.sublinear_tf = sublinear_tf
|
|
|
|
# Broadcast the TF-IDF parameters to the underlying transformer instance
|
|
# for easy grid search and repr
|
|
|
|
@property
|
|
def idf_(self):
|
|
"""Inverse document frequency vector, only defined if `use_idf=True`.
|
|
|
|
Returns
|
|
-------
|
|
ndarray of shape (n_features,)
|
|
"""
|
|
if not hasattr(self, "_tfidf"):
|
|
raise NotFittedError(
|
|
f"{self.__class__.__name__} is not fitted yet. Call 'fit' with "
|
|
"appropriate arguments before using this attribute."
|
|
)
|
|
return self._tfidf.idf_
|
|
|
|
@idf_.setter
|
|
def idf_(self, value):
|
|
if not self.use_idf:
|
|
raise ValueError("`idf_` cannot be set when `user_idf=False`.")
|
|
if not hasattr(self, "_tfidf"):
|
|
# We should support transferring `idf_` from another `TfidfTransformer`
|
|
# and therefore, we need to create the transformer instance it does not
|
|
# exist yet.
|
|
self._tfidf = TfidfTransformer(
|
|
norm=self.norm,
|
|
use_idf=self.use_idf,
|
|
smooth_idf=self.smooth_idf,
|
|
sublinear_tf=self.sublinear_tf,
|
|
)
|
|
self._validate_vocabulary()
|
|
if hasattr(self, "vocabulary_"):
|
|
if len(self.vocabulary_) != len(value):
|
|
raise ValueError(
|
|
"idf length = %d must be equal to vocabulary size = %d"
|
|
% (len(value), len(self.vocabulary))
|
|
)
|
|
self._tfidf.idf_ = value
|
|
|
|
def _check_params(self):
|
|
if self.dtype not in FLOAT_DTYPES:
|
|
warnings.warn(
|
|
"Only {} 'dtype' should be used. {} 'dtype' will "
|
|
"be converted to np.float64.".format(FLOAT_DTYPES, self.dtype),
|
|
UserWarning,
|
|
)
|
|
|
|
@_fit_context(prefer_skip_nested_validation=True)
|
|
def fit(self, raw_documents, y=None):
|
|
"""Learn vocabulary and idf from training set.
|
|
|
|
Parameters
|
|
----------
|
|
raw_documents : iterable
|
|
An iterable which generates either str, unicode or file objects.
|
|
|
|
y : None
|
|
This parameter is not needed to compute tfidf.
|
|
|
|
Returns
|
|
-------
|
|
self : object
|
|
Fitted vectorizer.
|
|
"""
|
|
self._check_params()
|
|
self._warn_for_unused_params()
|
|
self._tfidf = TfidfTransformer(
|
|
norm=self.norm,
|
|
use_idf=self.use_idf,
|
|
smooth_idf=self.smooth_idf,
|
|
sublinear_tf=self.sublinear_tf,
|
|
)
|
|
X = super().fit_transform(raw_documents)
|
|
self._tfidf.fit(X)
|
|
return self
|
|
|
|
def fit_transform(self, raw_documents, y=None):
|
|
"""Learn vocabulary and idf, return document-term matrix.
|
|
|
|
This is equivalent to fit followed by transform, but more efficiently
|
|
implemented.
|
|
|
|
Parameters
|
|
----------
|
|
raw_documents : iterable
|
|
An iterable which generates either str, unicode or file objects.
|
|
|
|
y : None
|
|
This parameter is ignored.
|
|
|
|
Returns
|
|
-------
|
|
X : sparse matrix of (n_samples, n_features)
|
|
Tf-idf-weighted document-term matrix.
|
|
"""
|
|
self._check_params()
|
|
self._tfidf = TfidfTransformer(
|
|
norm=self.norm,
|
|
use_idf=self.use_idf,
|
|
smooth_idf=self.smooth_idf,
|
|
sublinear_tf=self.sublinear_tf,
|
|
)
|
|
X = super().fit_transform(raw_documents)
|
|
self._tfidf.fit(X)
|
|
# X is already a transformed view of raw_documents so
|
|
# we set copy to False
|
|
return self._tfidf.transform(X, copy=False)
|
|
|
|
def transform(self, raw_documents):
|
|
"""Transform documents to document-term matrix.
|
|
|
|
Uses the vocabulary and document frequencies (df) learned by fit (or
|
|
fit_transform).
|
|
|
|
Parameters
|
|
----------
|
|
raw_documents : iterable
|
|
An iterable which generates either str, unicode or file objects.
|
|
|
|
Returns
|
|
-------
|
|
X : sparse matrix of (n_samples, n_features)
|
|
Tf-idf-weighted document-term matrix.
|
|
"""
|
|
check_is_fitted(self, msg="The TF-IDF vectorizer is not fitted")
|
|
|
|
X = super().transform(raw_documents)
|
|
return self._tfidf.transform(X, copy=False)
|
|
|
|
def _more_tags(self):
|
|
return {"X_types": ["string"], "_skip_test": True}
|