# Machine Learning and the Physical Sciences ## Applied Data Analysis and Machine Learning — FYS-STK3155/4155 Welcome. This Jupyter-book is the executable companion to the textbook *Machine Learning and the Physical Sciences: From discriminative methods to generative methods and reinforcement learning*. It covers the same material as the printed book, chapter for chapter, with every program in a cell you can edit and run. **Start with the [Introduction](introduction.ipynb).** It says what machine learning is taken to mean here, what the book aims to do, how the seventeen chapters fit together, which routes through them make sense, and what ethical obligations come with the material. Everything that used to be summarised on this page — the learning outcomes, the list of topics, the choice of programming language — is developed there properly. This page keeps only the practical matters: what you need to know beforehand, and what you need installed. ## How the material is organised The book is in five parts. Part I builds the mathematical and statistical basis, Part II the classical methods of statistical learning, Part III deep learning, Part IV generative modelling, and Part V looks towards reinforcement learning. A closing chapter draws the whole together and says where these methods are being taken in the sciences. Each chapter develops the theory with the algebra shown, checks every result that can be checked numerically against a program printed in the text, and closes with a summary and a graded set of exercises. Every number quoted in the text is produced by one of those programs, and every figure is generated by running it, so anything here can be reproduced on a laptop in minutes. Alongside the chapters you will find the weekly lecture notebooks, the weekly exercise sets and the project descriptions for the current semester. ## Prerequisites and background Basic knowledge of programming and of mathematics, with an emphasis on linear algebra. Knowledge of Python and/or C++ is strongly recommended, and some experience with Jupyter notebooks helps. The required courses are the equivalents of the University of Oslo mathematics courses MAT1100, MAT1110 and MAT1120, together with at least one of the corresponding programming courses INF1000/INF1110 or MAT-INF1100/MAT-INF1100L/BIOS1100/KJM-INF1100. Most universities now offer a basic, often compulsory, programming course in Python. We also recommend refreshing your knowledge of statistics and probability theory; Chapter 2 of this book is written to serve as that refresher. Computational work plays a central role and you are expected to work through the numerical examples and projects that illustrate the theory. We strongly recommend forming small project groups of two or three participants where possible. ## Required technologies Course participants are expected to have their own laptop. We use [Git](https://git-scm.com/) as version control software, and using a provider such as [GitHub](https://github.com/) or [GitLab](https://about.gitlab.com/) is strongly recommended. If Git is new to you, this [introduction](https://www.youtube.com/watch?v=RGOj5yH7evk) is a good starting point. We make extensive use of Python and its libraries. You can also use compiled languages such as C++, Rust, Julia or Fortran where speed matters — the book gives C++ and Fortran versions of several algorithms — but the focus of the lectures is on Python. If you have Python installed and are comfortable installing packages, the following will cover most of what is needed: ```bash pip install numpy scipy matplotlib ipython scikit-learn sympy pandas pillow ``` On macOS we recommend installing [Homebrew](https://brew.sh/) after Xcode, and then `brew install python3`. On Linux, `sudo apt-get install python3` or the equivalent for your distribution. ### Python distributions If you would rather not set up dependencies and paths yourself, [Anaconda](https://docs.anaconda.com/) is an open-source distribution of Python and R for large-scale data processing, predictive analytics and scientific computing, with package versions managed by `conda`. [Google Colab](https://colab.research.google.com/) is a free Jupyter notebook environment that requires no setup at all and runs entirely in the cloud. ### Useful Python libraries - [NumPy](https://www.numpy.org/) — large multi-dimensional arrays and matrices, with a large collection of mathematical functions to operate on them. Used in every chapter. - [SciPy](https://www.scipy.org/) — algorithms for mathematics, science and engineering built on NumPy. - [Matplotlib](https://matplotlib.org/) — 2D plotting, producing publication-quality figures. Every figure in this book is made with it. - [pandas](https://pandas.pydata.org/) — data structures and data analysis tools for labelled tabular data. - [scikit-learn](https://scikit-learn.org/stable/) — simple and efficient tools for machine learning and data mining; the reference implementation we compare our own code against in the classical chapters. - [PyTorch](https://pytorch.org/) and [TensorFlow](https://www.tensorflow.org/) — the two deep-learning frameworks. Chapters 10, 11, 13, 14, 15 and 17 each write the same model in both, and check the results against the implementation from scratch. - [JAX](https://jax.readthedocs.io/en/latest/index.html) — composable transformations of Python and NumPy programs: automatic differentiation, vectorisation, parallelisation and just-in-time compilation. It has largely replaced [Autograd](https://github.com/HIPS/autograd). - [SymPy](https://www.sympy.org/en/index.html) — symbolic mathematics, useful for checking a derivation by hand. - [Xarray](https://docs.xarray.dev/en/stable/) — labelled multi-dimensional arrays, convenient for scientific data sets. ## Using and citing this material All source files, programs and figures are freely available. You are encouraged to use the code, modify it, and include it in publications, thesis work and your own lectures. If you find it useful, a reference is appreciated: M. Hjorth-Jensen, *Machine Learning and the Physical Sciences*, University of Oslo.