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Topic Comparison Tool

The tool provides a bird’s-eye view of a text source. It takes a text and maps the words so that semantically and stylistically similar words are close to each other. This enables users to explore a text source like a geographical map. As similar words are close to each other, the user can visually identify clusters of topics that present in the book. Conceptually, it can be understood as a Fourier transformation for texts.

The tool can be used to compare different text sources, e.g. a summary and its source material or Wikipedia article revisions. To compare the topics, three different sets of words are computed: a source text topic set, a summary topic set, as well as the intersection set of both topic sets. A colour is assigned to each set of words. This enables the user to visually compare the different text sources and to see which topics are covered where. The user can explore the word map and zoom in and out. He or she can also toggle the visibility, i.e. show and hide, certain word sets.

This tool was presented at PyCon Sweden and PyData London.

The slides and video recordings can be found here:

How to use this

You can upload the frontend code and use it to explore the precomputed topic sets.

An online demo is available here:

Available precomputed topic sets:

(Copy and paste the link into the tool)

You can use the backend code to process your own files. Please note that the word2vec vectors are not included. You can generate them using the word2vec C tool, the Python gensim library, or download the vectors precomputed by Google.

How it works


In the pre-processing step, all sentences are tokenized to extract single words. The tokenization is done using the Penn Treebank Tokenizer implemented in the Natural Language Processing Toolkit (NLTK) for Python. Alternatively, this could also be achieved with a regular expression.

Using a hash map, all words are counted. Only unique words, i.e. the keys of the hash map, are taken into account for the dimensionality reduction. Not all unique words are taken into account. The 3000 most frequent English words according to a frequency list collected from Wikipedia are ignored to reduce the amount of data.

Word representations

For all unique non-frequent words, the word representation vectors are collected from the word2vec model via the gensim Python library. Each word is represented by a N-dimensional vector (N=300).

Dimensionality Reduction

The results of the word2vec vectors are projected down to 2D using the t-SNE Python implementation in scikit-learn.


After the dimensionality reduction, the vectors are written to a JSON file. The vectors are visualized using the D3.js Javascript data visualization library. Using D3.js, an interactive map was developed. With this map, the user can move around and zoom in and out.


2015 Hendrik Heuer

GNU General Public License 3

This program is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version. This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with this program. If not, see


Using word2vec and t-SNE to compare text sources.




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