Chapter 6

Neural Networks

IN THIS CHAPTER

Bullet Neural networks defined

Bullet Why and when to use neural networks

Bullet A neural network for the iris dataset

Bullet The nnet package

Bullet Neural networks in Rattle

Neural networks are a popular form of supervised machine learning. They’re popular because they’re widely applied in an array of areas, like speech recognition and image processing. Investors rely on these networks to recognize patterns in the stock market and decide whether to buy or sell. As the name indicates, their design reflects the structure and function of the nervous system.

Networks in the Nervous System

The nervous system consists of cells called neurons. Figure 6-1 shows a neuron on the left connected to three neurons on the right. The neuron on the left receives, through its dendrites, messages from other neurons. This neuron processes what it receives, and the result becomes a signal it sends along its axon. Through connections called synapses (yes, each one is a tiny gap), the signal ...

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