Overview

A high-performance topological machine learning toolbox in Python

giotto-tda is a high performance topological machine learning toolbox in Python built on top of scikit-learn and is distributed under the GNU AGPLv3 license. It is part of the Giotto family of open-source projects.

Guiding principles

  • Seamless integration with scikit-learn
    Strictly adhere to the scikit-learn API and development guidelines, inherit the strengths of that framework.
  • Code modularity
    Topological feature creation steps as transformers. Allow for the creation of a large number of topologically-powered machine learning pipelines.
  • Standardisation
    Implement the most successful techniques from the literature into a generic framework with a consistent API.
  • Innovation
    Improve on existing algorithms, and make new ones available in open source.
  • Performance
    For the most demanding computations, fall back to state-of-the-art C++ implementations, bound efficiently to Python. Vectorized code and implements multi-core parallelism (with joblib).
  • Data structures
    Support for tabular data, time series, graphs, and images.

30s guide to giotto-tda

_images/giotto-tda_workflow.png

For installation instructions, see the installation instructions.

The functionalities of giotto-tda are provided in scikit-learn–style transformers. This allows you to generate topological features from your data in a familiar way. Here is an example with the VietorisRipsPersistence transformer:

from gtda.homology import VietorisRipsPersistence
VR = VietorisRipsPersistence()

which computes topological summaries, called persistence diagrams, from collections of point clouds or weighted graphs, as follows:

diagrams = VR.fit_transform(point_clouds)

A plotting API allows for quick visual inspection of the outputs of many of giotto-tda’s transformers. To visualize the i-th output sample, run

diagrams = VR.plot(diagrams, sample=i)

You can create scalar or vector features from persistence diagrams using giotto-tda’s dedicated transformers. Here is an example with the PersistenceEntropy transformer:

from gtda.diagrams import PersistenceEntropy
PE = PersistenceEntropy()
features = PE.fit_transform(diagrams)

features is a two-dimensional numpy array. This is important to making this type of topological feature generation fit into a typical machine learning workflow from scikit-learn. In particular, topological feature creation steps can be fed to or used alongside models from scikit-learn, creating end-to-end pipelines which can be evaluated in cross-validation, optimised via grid-searches, etc.:

from sklearn.ensemble import RandomForestClassifier
from gtda.pipeline import make_pipeline
from sklearn.model_selection import train_test_split

X_train, X_valid, y_train, y_valid = train_test_split(point_clouds, labels)
RFC = RandomForestClassifier()
model = make_pipeline(VR, PE, RFC)
model.fit(X_train, y_train)
model.score(X_valid, y_valid)

giotto-tda also implements the Mapper algorithm as a highly customisable scikit-learn Pipeline, and provides simple plotting functions for visualizing output Mapper graphs and have real-time interaction with the pipeline parameters:

from gtda.mapper import make_mapper_pipeline
from sklearn.decomposition import PCA
from sklearn.cluster import DBSCAN

pipe = make_mapper_pipeline(filter_func=PCA(), clusterer=DBSCAN())
plot_interactive_mapper_graph(pipe, data)

Resources

Tutorials and examples

We provide a number of tutorials and examples, which offer:

  • quick start guides to the API;

  • in-depth examples showcasing more of the library’s features;

  • intuitive explanations of topological techniques.

Use cases

A selection of use cases for giotto-tda is collected at this page. Please note, however, that some of these were written for past versions of giotto-tda. In some cases, only small modifications are needed to run them on recent versions, while in others it is best to install the relevant past version of giotto-tda (preferably in a fresh environmnent). In a couple of cases, the legacy giotto-learn or giotto-learn-nightly will be needed.

What’s new

Major Features and Improvements

  • The latest changes made to the ripser.py submodule have been pulled (#530, see also #532). This includes in particular the performance improvements to the C++ backend submitted by Julian Burella Pérez via scikit-tda/ripser.py#106. The developer installation now includes a new dependency in robinhood hashmap. These changes do not affect functionality.

  • The example notebook classifying_shapes.ipynb has been modified and improved (#523).

  • The tutorial previously called time_series_classification.ipynb has been split into an introductory tutorial on the Takens embedding ideas (topology_time_series.ipynb) and an example notebook on gravitational wave detection (gravitational_waves_detection.ipynb) which presents a time series classification task (#529).

  • The documentation for PairwiseDistance has been improved (#525).

Bug Fixes

  • Timeout deadlines for some of the hypothesis tests have been increased to make them less flaky (#531).

Backwards-Incompatible Changes

  • Due to poor support for brew in the macOS 10.14 virtual machines by Azure, the CI for macOS systems is now run on 10.15 virtual machines and 10.14 is no longer supported by the wheels (#527)

Thanks to our Contributors

This release contains contributions from many people:

Julian Burella Pérez, Umberto Lupo, Lewis Tunstall, Wojciech Reise, and Rayna Andreeva.

We are also grateful to all who filed issues or helped resolve them, asked and answered questions, and were part of inspiring discussions.