BERTopic

BERTopic is a topic modeling technique that leverages 🤗 transformers and c-TF-IDF to create dense clusters allowing for easily interpretable topics whilst keeping important words in the topic descriptions.

BERTopic supports all kinds of topic modeling techniques:

Guided	Supervised	Semi-supervised
Manual	Multi-topic distributions	Hierarchical
Class-based	Dynamic	Online/Incremental
Multimodal	Multi-aspect	Text Generation/LLM
Merge Models

Corresponding medium posts can be found here, here and here. For a more detailed overview, you can read the paper or see a brief overview.

Installation

Installation, with sentence-transformers, can be done using pypi:

pip install bertopic

If you want to install BERTopic with other embedding models, you can choose one of the following:

# Choose an embedding backend
pip install bertopic[flair, gensim, spacy, use]

# Topic modeling with images
pip install bertopic[vision]

Getting Started

For an in-depth overview of the features of BERTopic you can check the full documentation or you can follow along with one of the examples below:

Name	Link
BERTopic - Best Practices
Topic Modeling with BERTopic
(Custom) Embedding Models in BERTopic
Advanced Customization in BERTopic
(semi-)Supervised Topic Modeling with BERTopic
Dynamic Topic Modeling with Trump's Tweets
New - Topic Modeling on Large Data
New - Topic Modeling with Llama 2 🦙
Topic Modeling arXiv Abstracts

Quick Start

We start by extracting topics from the well-known 20 newsgroups dataset containing English documents:

from bertopic import BERTopic
from sklearn.datasets import fetch_20newsgroups
 
docs = fetch_20newsgroups(subset='all',  remove=('headers', 'footers', 'quotes'))['data']

topic_model = BERTopic()
topics, probs = topic_model.fit_transform(docs)

After generating topics and their probabilities, we can access all of the topics together with their topic representations:

>>> topic_model.get_topic_info()

Topic	Count	Name
-1	4630	-1_can_your_will_any
0	693	49_windows_drive_dos_file
1	466	32_jesus_bible_christian_faith
2	441	2_space_launch_orbit_lunar
3	381	22_key_encryption_keys_encrypted
...

The -1 topic refers to all outlier documents and are typically ignored. Each word in a topic describes the underlying theme of that topic and can be used for interpreting that topic. Next, let's take a look at the most frequent topic that was generated:

>>> topic_model.get_topic(0)

[('windows', 0.006152228076250982),
 ('drive', 0.004982897610645755),
 ('dos', 0.004845038866360651),
 ('file', 0.004140142872194834),
 ('disk', 0.004131678774810884),
 ('mac', 0.003624848635985097),
 ('memory', 0.0034840976976789903),
 ('software', 0.0034415334250699077),
 ('email', 0.0034239554442333257),
 ('pc', 0.003047105930670237)]

Using .get_document_info, we can also extract information on a document level, such as their corresponding topics, probabilities, whether they are representative documents for a topic, etc.:

>>> topic_model.get_document_info(docs)

Document                               Topic	Name	                        Top_n_words                     Probability    ...
I am sure some bashers of Pens...	0	0_game_team_games_season	game - team - games...	        0.200010       ...
My brother is in the market for...      -1     -1_can_your_will_any	        can - your - will...	        0.420668       ...
Finally you said what you dream...	-1     -1_can_your_will_any	        can - your - will...            0.807259       ...
Think! It's the SCSI card doing...	49     49_windows_drive_dos_file	windows - drive - docs...	0.071746       ...
1) I have an old Jasmine drive...	49     49_windows_drive_dos_file	windows - drive - docs...	0.038983       ...

🔥 Tip: Use BERTopic(language="multilingual") to select a model that supports 50+ languages.

Fine-tune Topic Representations

In BERTopic, there are a number of different topic representations that we can choose from. They are all quite different from one another and give interesting perspectives and variations of topic representations. A great start is KeyBERTInspired, which for many users increases the coherence and reduces stopwords from the resulting topic representations:

from bertopic.representation import KeyBERTInspired

# Fine-tune your topic representations
representation_model = KeyBERTInspired()
topic_model = BERTopic(representation_model=representation_model)

However, you might want to use something more powerful to describe your clusters. You can even use ChatGPT or other models from OpenAI to generate labels, summaries, phrases, keywords, and more:

import openai
from bertopic.representation import OpenAI

# Fine-tune topic representations with GPT
openai.api_key = "sk-..."
representation_model = OpenAI(model="gpt-3.5-turbo", chat=True)
topic_model = BERTopic(representation_model=representation_model)

🔥 Tip: Instead of iterating over all of these different topic representations, you can model them simultaneously with multi-aspect topic representations in BERTopic.

Visualizations

After having trained our BERTopic model, we can iteratively go through hundreds of topics to get a good understanding of the topics that were extracted. However, that takes quite some time and lacks a global representation. Instead, we can use one of the many visualization options in BERTopic. For example, we can visualize the topics that were generated in a way very similar to LDAvis:

topic_model.visualize_topics()

Modularity

By default, the main steps for topic modeling with BERTopic are sentence-transformers, UMAP, HDBSCAN, and c-TF-IDF run in sequence. However, it assumes some independence between these steps which makes BERTopic quite modular. In other words, BERTopic not only allows you to build your own topic model but to explore several topic modeling techniques on top of your customized topic model:

BERTopicOverview.mp4

You can swap out any of these models or even remove them entirely. The following steps are completely modular:

1. Embedding documents
2. Reducing dimensionality of embeddings
3. Clustering reduced embeddings into topics
4. Tokenization of topics
5. Weight tokens
6. Represent topics with one or multiple representations

Functionality

BERTopic has many functions that quickly can become overwhelming. To alleviate this issue, you will find an overview of all methods and a short description of its purpose.

Common

Below, you will find an overview of common functions in BERTopic.

Method	Code
Fit the model	.fit(docs)
Fit the model and predict documents	.fit_transform(docs)
Predict new documents	.transform([new_doc])
Access single topic	.get_topic(topic=12)
Access all topics	.get_topics()
Get topic freq	.get_topic_freq()
Get all topic information	.get_topic_info()
Get all document information	.get_document_info(docs)
Get representative docs per topic	.get_representative_docs()
Update topic representation	.update_topics(docs, n_gram_range=(1, 3))
Generate topic labels	.generate_topic_labels()
Set topic labels	.set_topic_labels(my_custom_labels)
Merge topics	.merge_topics(docs, topics_to_merge)
Reduce nr of topics	.reduce_topics(docs, nr_topics=30)
Reduce outliers	.reduce_outliers(docs, topics)
Find topics	.find_topics("vehicle")
Save model	.save("my_model", serialization="safetensors")
Load model	BERTopic.load("my_model")
Get parameters	.get_params()

Attributes

After having trained your BERTopic model, several attributes are saved within your model. These attributes, in part, refer to how model information is stored on an estimator during fitting. The attributes that you see below all end in _ and are public attributes that can be used to access model information.

Attribute	Description
.topics_	The topics that are generated for each document after training or updating the topic model.
.probabilities_	The probabilities that are generated for each document if HDBSCAN is used.
.topic_sizes_	The size of each topic
.topic_mapper_	A class for tracking topics and their mappings anytime they are merged/reduced.
.topic_representations_	The top n terms per topic and their respective c-TF-IDF values.
.c_tf_idf_	The topic-term matrix as calculated through c-TF-IDF.
.topic_aspects_	The different aspects, or representations, of each topic.
.topic_labels_	The default labels for each topic.
.custom_labels_	Custom labels for each topic as generated through .set_topic_labels.
.topic_embeddings_	The embeddings for each topic if embedding_model was used.
.representative_docs_	The representative documents for each topic if HDBSCAN is used.

Variations

There are many different use cases in which topic modeling can be used. As such, several variations of BERTopic have been developed such that one package can be used across many use cases.

Method	Code
Topic Distribution Approximation	.approximate_distribution(docs)
Online Topic Modeling	.partial_fit(doc)
Semi-supervised Topic Modeling	.fit(docs, y=y)
Supervised Topic Modeling	.fit(docs, y=y)
Manual Topic Modeling	.fit(docs, y=y)
Multimodal Topic Modeling	.fit(docs, images=images)
Topic Modeling per Class	.topics_per_class(docs, classes)
Dynamic Topic Modeling	.topics_over_time(docs, timestamps)
Hierarchical Topic Modeling	.hierarchical_topics(docs)
Guided Topic Modeling	BERTopic(seed_topic_list=seed_topic_list)
Merge Multiple Models	BERTopic.merge_models([topic_model_1, topic_model_2])

Visualizations

Evaluating topic models can be rather difficult due to the somewhat subjective nature of evaluation. Visualizing different aspects of the topic model helps in understanding the model and makes it easier to tweak the model to your liking.

Method	Code
Visualize Topics	.visualize_topics()
Visualize Documents	.visualize_documents()
Visualize Document Hierarchy	.visualize_hierarchical_documents()
Visualize Topic Hierarchy	.visualize_hierarchy()
Visualize Topic Tree	.get_topic_tree(hierarchical_topics)
Visualize Topic Terms	.visualize_barchart()
Visualize Topic Similarity	.visualize_heatmap()
Visualize Term Score Decline	.visualize_term_rank()
Visualize Topic Probability Distribution	.visualize_distribution(probs[0])
Visualize Topics over Time	.visualize_topics_over_time(topics_over_time)
Visualize Topics per Class	.visualize_topics_per_class(topics_per_class)

Citation

To cite the BERTopic paper, please use the following bibtex reference:

@article{grootendorst2022bertopic,
  title={BERTopic: Neural topic modeling with a class-based TF-IDF procedure},
  author={Grootendorst, Maarten},
  journal={arXiv preprint arXiv:2203.05794},
  year={2022}
}