TOM (TOpic Modeling) is a Python 3 library for topic modeling and browsing, licensed under the MIT license. Its objective is to allow for an efficient analysis of a text corpus from start to finish, via the discovery of latent topics. To this end, TOM features functions for preparing and vectorizing a text corpus. It also offers a common interface for two topic models (namely LDA using either variational inference or Gibbs sampling, and NMF using alternating least-square with a projected gradient method), and implements three state-of-the-art methods for estimating the optimal number of topics to model a corpus. What is more, TOM constructs an interactive Web-based browser that makes it easy to explore a topic model and the related corpus.
Vector space modeling
- Feature selection based on word frequency
- Latent Dirichlet Allocation
- Standard variational Bayesian inference (Latent Dirichlet Allocation. Blei et al, 2003)
- Online variational Bayesian inference (Online learning for Latent Dirichlet Allocation. Hoffman et al, 2010)
- Collapsed Gibbs sampling (Finding scientific topics. Griffiths & Steyvers, 2004)
- Non-negative Matrix Factorization (NMF)
- Alternating least-square with a projected gradient method (Projected gradient methods for non-negative matrix factorization. Lin, 2007)
Estimating the optimal number of topics
- Stability analysis (How many topics? Stability analysis for topic models. Greene et al, 2014)
- Spectral analysis (On finding the natural number of topics with latent dirichlet allocation: Some observations. Arun et al, 2010)
- Consensus-based analysis (Metagenes and molecular pattern discovery using matrix factorization. Brunet et al, 2004)
We recommend you to install Anaconda (https://www.continuum.io) which will automatically install most of the required dependencies (i.e. pandas, numpy, scipy, scikit-learn, matplotlib, flask). You should then install the lda module (pip install lda). Eventually, clone or download this repo and run the following command:
python setup.py install
Or install it directly either from PyPi:
pip install tom_lib
or from Conda Cloud:
conda install -c psoriano tom_lib
We provide two sample programs, topic_model.py (which shows you how to load and prepare a corpus, estimate the optimal number of topics, infer the topic model and then manipulate it) and topic_model_browser.py (which shows you how to generate a topic model browser to explore a corpus), to help you get started using TOM.
Load and prepare a textual corpus
A corpus is a TSV (tab separated values) file describing documents, formatted as follows: a document per line, with at least three columns, namely id (a number), title (a short text) and text (the full content of the document), e.g.:
id title text 1 Document 1's title This is the full content of document 1. 2 Document 2's title This is the full content of document 2. etc.
The following code snippet shows how to load a corpus of French documents and vectorize them using tf-idf with unigrams.
corpus = Corpus(source_file_path='input/raw_corpus.csv', language='french', vectorization='tfidf', n_gram=1, max_relative_frequency=0.8, min_absolute_frequency=4) print('corpus size:', corpus.size) print('vocabulary size:', len(corpus.vocabulary)) print('Vector representation of document 0:\n', corpus.vector_for_document(0))
Instantiate a topic model and infer topics
It is possible to instantiate a NMF or LDA object then infer topics.
topic_model = NonNegativeMatrixFactorization(corpus) topic_model.infer_topics(num_topics=15)
LDA (using either the standard variational Bayesian inference or Gibbs sampling):
topic_model = LatentDirichletAllocation(corpus) topic_model.infer_topics(num_topics=15, algorithm='variational')
topic_model = LatentDirichletAllocation(corpus) topic_model.infer_topics(num_topics=15, algorithm='gibbs')
Instantiate a topic model and estimate the optimal number of topics
Here we instantiate a NMF object, then generate plots with the three metrics for estimating the optimal number of topics.
topic_model = NonNegativeMatrixFactorization(corpus) viz = Visualization(topic_model) viz.plot_greene_metric(min_num_topics=5, max_num_topics=50, tao=10, step=1, top_n_words=10) viz.plot_arun_metric(min_num_topics=5, max_num_topics=50, iterations=10) viz.plot_brunet_metric(min_num_topics=5, max_num_topics=50, iterations=10)
Save/load a topic model
To allow reusing previously learned topics models, TOM can save them on disk, as shown below.
utils.save_topic_model(topic_model, 'output/NMF_15topics.tom') topic_model = utils.load_topic_model('output/NMF_15topics.tom')
Print information about a topic model
This code excerpt illustrates how one can manipulate a topic model, e.g. get the topic distribution for a document or the word distribution for a topic.
print('\nTopics:') topic_model.print_topics(num_words=10) print('\nTopic distribution for document 0:', topic_model.topic_distribution_for_document(0)) print('\nMost likely topic for document 0:', topic_model.most_likely_topic_for_document(0)) print('\nFrequency of topics:', topic_model.topics_frequency()) print('\nTop 10 most relevant words for topic 2:', topic_model.top_words(2, 10))