Book Image

Python: Advanced Guide to Artificial Intelligence

By : Giuseppe Bonaccorso, Rajalingappaa Shanmugamani
Book Image

Python: Advanced Guide to Artificial Intelligence

By: Giuseppe Bonaccorso, Rajalingappaa Shanmugamani

Overview of this book

This Learning Path is your complete guide to quickly getting to grips with popular machine learning algorithms. You'll be introduced to the most widely used algorithms in supervised, unsupervised, and semi-supervised machine learning, and learn how to use them in the best possible manner. Ranging from Bayesian models to the MCMC algorithm to Hidden Markov models, this Learning Path will teach you how to extract features from your dataset and perform dimensionality reduction by making use of Python-based libraries. You'll bring the use of TensorFlow and Keras to build deep learning models, using concepts such as transfer learning, generative adversarial networks, and deep reinforcement learning. Next, you'll learn the advanced features of TensorFlow1.x, such as distributed TensorFlow with TF clusters, deploy production models with TensorFlow Serving. You'll implement different techniques related to object classification, object detection, image segmentation, and more. By the end of this Learning Path, you'll have obtained in-depth knowledge of TensorFlow, making you the go-to person for solving artificial intelligence problems This Learning Path includes content from the following Packt products: • Mastering Machine Learning Algorithms by Giuseppe Bonaccorso • Mastering TensorFlow 1.x by Armando Fandango • Deep Learning for Computer Vision by Rajalingappaa Shanmugamani
Table of Contents (31 chapters)
Title Page
About Packt
Contributors
Preface
19
Tensor Processing Units
Index

Label propagation based on Markov random walks


The goal of this algorithm proposed by Zhu and Ghahramani is to find the probability distribution of target labels for unlabeled samples given a mixed dataset. This objective is achieved through the simulation of a stochastic process, where each unlabeled sample walks through the graph until it reaches a stationary absorbing state, a labeled sample where it stops acquiring the corresponding label. The main difference with other similar approaches is that in this case, we consider the probability of reaching a labeled sample. In this way, the problem acquires a closed form and can be easily solved.

The first step is to always build a k-nearest neighbors graph with all N samples, and define a weight matrix W based on an RBF kernel:

Wij = 0 is xiand xj are not neighbors and Wii = 1. The transition probability matrix, similarly to the Scikit-Learn label propagation algorithm, is built as:

In a more compact way, it can be rewritten as P = D-1W. If...