Book Image

Data Science Using Python and R

By : Chantal D. Larose, Daniel T. Larose
Book Image

Data Science Using Python and R

By: Chantal D. Larose, Daniel T. Larose

Overview of this book

Data science is hot. Bloomberg named a data scientist as the ‘hottest job in America’. Python and R are the top two open-source data science tools using which you can produce hands-on solutions to real-world business problems, using state-of-the-art techniques. Each chapter in the book presents step-by-step instructions and walkthroughs for solving data science problems using Python and R. You’ll learn how to prepare data, perform exploratory data analysis, and prepare to model the data. As you progress, you’ll explore what are decision trees and how to use them. You’ll also learn about model evaluation, misclassification costs, naïve Bayes classification, and neural networks. The later chapters provide comprehensive information about clustering, regression modeling, dimension reduction, and association rules mining. The book also throws light on exciting new topics, such as random forests and general linear models. The book emphasizes data-driven error costs to enhance profitability, which avoids the common pitfalls that may cost a company millions of dollars. By the end of this book, you’ll have enough knowledge and confidence to start providing solutions to data science problems using R and Python.
Table of Contents (20 chapters)
Free Chapter
1
ABOUT THE AUTHORS
17
INDEX
18
END USER LICENSE AGREEMENT

9.2 THE NEURAL NETWORK STRUCTURE

Let us examine the simple neural network shown in Figure 9.2.

Schematic displaying the simple example of a neural network starting from the input to hidden leading to output layer represented by ovals labeled node 1, 2, and 3 to node A and B leading to node Z.

Figure 9.2 Simple example of a neural network.

A neural network consists of a layered, feedforward, completely connected network of artificial neurons or nodes.

  • The feedforward nature of the network restricts the network to a single direction of flow and does not allow looping or cycling.
  • Most networks consist of three layers: an input layer, a hidden layer, and an output layer.
    • There may be more than one hidden layer, although most networks contain only one, which is sufficient for most purposes.
  • The neural network is completely connected, meaning that every node in a given layer is connected to every node in adjoining layers, although not to other nodes in the same layer.
    • Each connection between nodes has a weight (e.g. W1A) associated with it.
    • At initialization, these weights are randomly assigned to values between 0 and 1.

The number of input nodes depends on the number and type...