Automated Machine Learning – Bayesian Optimization, Meta-Learning & Applications

Automating machine learning by providing techniques that autonomously find the best algorithm, hyperparameter configuration and preprocessing is helpful for both researchers and practitioners. Therefore, it is not surprising that automated machine learning has become a very interesting field of research. Bayesian optimization has proven to be a very successful tool for automated machine learning. In the first part of the thesis we present different approaches to improve Bayesian optimization by means of transfer learning. We present three different ways of considering meta-knowledge in Bayesian optimization, i.e. search space pruning, initialization and transfer surrogate models. Finally, we present a general framework for Bayesian optimization combined with meta-learning and conduct a comparison among existing work on two different meta-data sets. A conclusion is that in particular the meta-target driven approaches provide better results. Choosing algorithm configurations based on the improvement on the meta-knowledge combined with the expected improvement yields best results. The second part of this thesis is more application-oriented. Bayesian optimization is applied to large data sets and used as a tool to participate in machine learning challenges. We compare its autonomous performance and its performance in combination with a human expert. At two ECML-PKDD Discovery Challenges, we are able to show that automated machine learning outperforms human machine learning experts. Finally, we present an approach that automates the process of creating an ensemble of several layers, different algorithms and hyperparameter configurations. These kinds of ensembles are jokingly called Frankenstein ensembles and proved their benefit on versatile data sets in many machine learning challenges. We compare our approach Automatic Frankensteining with the current state of the art for automated machine learning on 80 different data sets and can show that it outperforms them on the majority using the same training time. Furthermore, we compare Automatic Frankensteining on a large-scale data set to more than 3,500 machine learning expert teams and are able to outperform more than 3,000 of them within 12 CPU hours.


Comprehensive Guide to build a Recommendation Engine from scratch (in Python)

In today´s world, every customer is faced with multiple choices. For example, If I´m looking for a book to read without any specific idea of what I want, there´s a wide range of possibilities how my search might pan out. I might waste a lot of time browsing around on the internet and trawling through various sites hoping to strike gold. I might look for recommendations from other people. But if there was a site or app which could recommend me books based on what I have read previously, that would be a massive help. Instead of wasting time on various sites, I could just log in and voila! 10 recommended books tailored to my taste. This is what recommendation engines do and their power is being harnessed by most businesses these days. From Amazon to Netflix, Google to Goodreads, recommendation engines are one of the most widely used applications of machine learning techniques. In this article, we will cover various types of recommendation engine algorithms and fundamentals of creating them in Python. We will also see the mathematics behind the workings of these algorithms. Finally, we will create our own recommendation engine using matrix factorization.


Machine Learning and NLP using R: Topic Modeling and Music Classification

In this tutorial, you will build four models using Latent Dirichlet Allocation (LDA) and K-Means clustering machine learning algorithms.


Top Python Libraries for Machine Learning

Today, Python is one of the most popular programming languages and it has replaced many languages in the industry. There are various reasons for its popularity and one of them is that python has a large collection of libraries. With python, the data scientists need not spend all the day debugging. They just need to invest time in determining which python library works best for their ongoing projects. So, what is a Python Library It is a collection of methods and functions that enable you to carry out a lot of actions without the need for writing your code.


Lda2vec-Tensorflow

Tensorflow 1.5 implementation of Chris Moody’s Lda2vec


Automated Feature Engineering in Python

Machine learning is increasingly moving from hand-designed models to automatically optimized pipelines using tools such as H20, TPOT, and auto-sklearn. These libraries, along with methods such as random search, aim to simplify the model selection and tuning parts of machine learning by finding the best model for a dataset with little to no manual intervention. However, feature engineering, an arguably more valuable aspect of the machine learning pipeline, remains almost entirely a human labor. Feature engineering, also known as feature creation, is the process of constructing new features from existing data to train a machine learning model. This step can be more important than the actual model used because a machine learning algorithm only learns from the data we give it, and creating features that are relevant to a task is absolutely crucial (see the excellent paper ‘A Few Useful Things to Know about Machine Learning’). Typically, feature engineering is a drawn-out manual process, relying on domain knowledge, intuition, and data manipulation. This process can be extremely tedious and the final features will be limited both by human subjectivity and time. Automated feature engineering aims to help the data scientist by automatically creating many candidate features out of a dataset from which the best can be selected and used for training. In this article, we will walk through an example of using automated feature engineering with the featuretools Python library. We will use an example dataset to show the basics (stay tuned for future posts using real-world data). The complete code for this article is available on GitHub.


How Can Neural Network Similarity Help Us Understand Training and Generalization?

In order to solve tasks, deep neural networks (DNNs) progressively transform input data into a sequence of complex representations (i.e., patterns of activations across individual neurons). Understanding these representations is critically important, not only for interpretability, but also so that we can more intelligently design machine learning systems. However, understanding these representations has proven quite difficult, especially when comparing representations across networks. In a previous post, we outlined the benefits of Canonical Correlation Analysis (CCA) as a tool for understanding and comparing the representations of convolutional neural networks (CNNs), showing that they converge in a bottom-up pattern, with early layers converging to their final representations before later layers over the course of training.


Learn Machine Learning

This 29-part course consists of tutorials on ML concepts and algorithms, as well as end-to-end follow-along ML examples, quizzes, and hands-on projects. You can think of this course as a ‘Free Online Nano Book’.


Detecting Sarcasm with Deep Convolutional Neural Networks

This paper addresses a key NLP problem known as sarcasm detection using a combination of models based on convolutional neural networks (CNNs). Detection of sarcasm is important in other areas such as affective computing and sentiment analysis because such expressions can flip the polarity of a sentence.


Deep Learning Best Practices (1) – Weight Initialization

As a beginner at deep learning, one of the things I realized is that there isn´t much online documentation that covers all the deep learning tricks in one place. There are lots of small best practices, ranging from simple tricks like initializing weights, regularization to slightly complex techniques like cyclic learning rates that can make training and debugging neural nets easier and efficient. This inspired me to write this series of blogs where I will cover as many nuances as I can to make implementing deep learning simpler for you. While writing this blog, the assumption is that you have a basic idea of how neural networks are trained. An understanding of weights, biases, hidden layers, activations and activation functions will make the content clearer. I would recommend this course if you wish to build a basic foundation of deep learning. Note – Whenever I refer to layers of a neural network, it implies the layers of a simple neural network, i.e. the fully connected layers. Of course some of the methods I talk about apply to convolutional and recurrent neural networks as well. In this blog I am going to talk about the issues related to initialization of weight matrices and ways to mitigate them. Before that, let´s just cover some basics and notations that we will be using going forward.


Non-Linear Model in R Exercises

A mechanistic model for the relationship between x and y sometimes needs parameter estimation. When model linearisation does not work,we need to use non-linear modelling.


Neural Networks Are Essentially Polynomial Regression

You may be interested in my new arXiv paper, joint work with Xi Cheng, an undergraduate at UC Davis (now heading to Cornell for grad school); Bohdan Khomtchouk, a post doc in biology at Stanford; and Pete Mohanty, a Science, Engineering & Education Fellow in statistics at Stanford. The paper is of a provocative nature, and we welcome feedback.


Reading and analysing log files in the RRD database format

I have frequent conversations with R champions and Systems Administrators responsible for R, in which they ask how they can measure and analyze the usage of their servers. Among the many solutions to this problem, one of the my favourites is to use an RRD database and RRDtool.


RRDtool

RRDtool is the OpenSource industry standard, high performance data logging and graphing system for time series data. RRDtool can be easily integrated in shell scripts, perl, python, ruby, lua or tcl applications.
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