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In the field of ML, Reinforcement Learning was developed by John Andreae in the year 1963 when he invented a system called Stella [27]. It is a dynamic approach that works on the concept of feedbacks [28–31]. Reinforcement for a machine is the reward that it receives upon acting in the environment. When the machine acts on its environment, it receives some evaluation on its actions which is called reinforcement but is not told of which action is the correct one for achieving the goal. In this, the machine’s utility is defined by the feedback function [32]. The objective is to maximize the expected feedback. The block diagram of reinforcement learning is shown below in Figure 1.6.

The above figure tries to present that, a machine at first performs some actions in the environment. Once the actions are performed, then the machine starts to receive the feedbacks. The collected feedbacks may be positive or negative type. The positive feedbacks are kept inside the machines as knowledge. The machine tries to learn from the negative feedback so that in future such an incident may not happen again. Another important aspect of reinforcement learning is the state. The state also provides the input based on the situation to the machine for learning purposes.

Figure 1.6 Block diagram of reinforcement learning.

A few points of reinforcement learning are as follows:

 The Input of the Reinforcement Learning Process: Initial state

 The Output of the Reinforcement Learning Process: Diversified solutions can be present, depending on the feedbacks obtained

 The training process is purely based on input.

 This Reinforcement Learning model is a continuous process.

 The best solution for this reinforcement learning is the maximum positive feedback.

An example of reinforcement learning could of a person who is suffering from high cholesterol and high blood pressure. He visits his family doctor and requests a medication regarding the same. After analyzing the symptoms, the doctor prescribed a diet chart and a set of medicines to minimize the cholesterol level and blood pressure. He took the medicines and felt better. Here, the patient gets positive feedback in the form of the results of the medication provided by the doctor. Now, the patient will be motivated and will consume only low-fat and low-sodium diet to keep down the levels of blood pressure & cholesterol. If the levels did not go down then the patient will ask the doctor about the same and more tests will be considered for the lowering of the parameters that are required to evaluate the heart of the patient.