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Feature selection methods for Text Classification

Project description


This project provides a set filter methods for feature selection applied to text classification.

Currently the following methods are available:

- ALOFT - At Least One FeaTure `[1] <>`_
- MFD - Maximum f Features per Document `[2] <>`_
- MFDR - Maximum f Features per Document-Reduced `[2] <>`_
- cMFDR - Class-dependent Maximum f Features per Document-Reduced `[3] <>`_
- AFSA - Automatic Features Subsets Analyzer `[4] <>`_

The package can be installed using pip:

``pip install featselection``

The code is tested to work with Python 3.6. The dependency requirements are:

* numpy
* scipy
* pandas
* scikit-learn

These dependencies are automatically installed using the pip command above.


In this example, we show the use MFD.

.. code-block:: python3

import numpy as np

from sklearn.metrics import accuracy_score
from sklearn.feature_selection import chi2
from sklearn.naive_bayes import MultinomialNB
from sklearn.datasets import fetch_20newsgroups
from sklearn.model_selection import StratifiedKFold
from sklearn.feature_extraction.text import CountVectorizer

from filters import MFD

# Load data
cats = ['', '', '', 'soc.religion.christian', 'talk.politics.misc']
newsgroups = fetch_20newsgroups(categories=cats)

# Pre-processing: Transform texts to Bag-of-Words and remove stopwords
vectorizer = CountVectorizer(stop_words='english')
vectors = vectorizer.fit_transform(

# 10-fold stratified cross validation
skf = StratifiedKFold(n_splits=10, shuffle=True, random_state=42)
accuracy_results = []

for train_index, test_index in skf.split(vectors,
# Train
my_filter = MFD(10, chi2)
X_train = my_filter.fit_transform(vectors[train_index],[train_index])
clf = MultinomialNB(),[train_index])

# Test
X_test = my_filter.transform(vectors[test_index])
predicted = clf.predict(X_test)

# Evaluate
accuracy_results.append(accuracy_score([test_index], predicted))

# Output averaged accuracy
print('Mean accuracy = {0} ({1})'.format(np.mean(accuracy_results), np.std(accuracy_results)))


`[1] <>`_ Pinheiro, Roberto HW, et al. "A global-ranking local feature selection method for text categorization." Expert Systems with Applications 39.17 (2012): 12851-12857.

`[2] <>`_ Pinheiro, Roberto HW, et al. "Data-driven global-ranking local feature selection methods for text categorization." Expert Systems with Applications 42.4 (2015): 1941-1949.

`[3] <>`_ Fragoso, Rogério CP, et al. "Class-dependent feature selection algorithm for text categorization." 2016 International Joint Conference on Neural Networks (IJCNN). IEEE, 2016.

`[4] <>`_ Fragoso, Rogério CP, et al. "A method for automatic determination of the feature vector size for text categorization." 2016 5th Brazilian Conference on Intelligent Systems (BRACIS). IEEE, 2016.

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