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Fundamentals to Reinforcement Learning- its Characteristics, Elements, and Applications

  • Neelam Tyagi
  • Nov 13, 2019
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In childhood, we got admired or praised by elders, they motivate us with different things, like, some gifts were given, they appreciated us, or even we also got rewarded. Yeah !!! We learn things, we experienced things by learning. Understand it, from good things or actions we learn and get rewards, opposite of that from bad actions we learn and get experience but never get a reward.


Even though the experience itself stands as a reward. We, human beings always try to learn or experience something new or adventurous. Don’t you wonder to learn something new approach for rewarding, even most interesting let’s learn how to reward machines for their good or bad actions? This blog will cover the introductory outline of reinforcement learning, its difference with other sorts of machine learning methodologies.


“How to learn new skills?”, sometimes you find it simple and sometimes a single step towards lead becomes difficult without having any prior experience. Irrespective of skills, the first step in learning is making interaction with the environment. Whether you are learning to cook food or a child learns to speak, the learning is based on the interaction with the environment. The most fundamental pace in learning with the interaction-based environment is crucial and immense.


Supervised learning, Unsupervised Learning, and Reinforcement learning are major areas of Machine learning domain, you must have read about Machine Learning in our previous blogs. Starting with the basic introduction of Reinforcement Learning, it is all about to exert suitable actions or decisions to maximize the reward for an appropriate condition. Many software and machine models vigorously use it to get the best possible way or action in a specific situation.


The reinforcement learning algorithm, model, or agent, learns by having interaction with its environment, the agent obtains rewards by performing correctly and also get penalties by performing incorrectly. The agent understands without having mediation with the human by making greater rewards and minimizing his penalties. The reinforcement learning algorithm operates combinedly with the system of rewards and punishments.


Consider the example, a scenario with an agent, a path with water, a fire path. As we learn that the reinforcement learning agent works on the system of rewards and penalties, I am simplifying here more working methodology of the reinforcement learning algorithm.


An agent interacts with its environment and learns, it either gains a reward or gets a penalty.

A scenario of the interaction of an agent with the environment.


If the agent chooses the fire path then rewards get subtracted and an agent must try to learn that it should avoid the fire path, on the other hand, if an agent chooses to the path with water then rewards are given and an agent learns that water path is safe and secure. Finally, the agent learns which path to be taken and which is not.


Some common terminologies for Reinforcement learning;


  • Agent: It is an imagined character that performs different episodes of actions in an environment to have some rewards or penalties.

  • Environment: A synopsis that an agent has to face in order to get experience.

  • Reward: A critical advantage provided back to an agent when it performs specific actions or tasks.

  • State: It signifies the current condition yielded by the environment.

  • Policy: It is a plan, or simply strategy, that implemented by the agent to determine the next action based on the current state.

  • Value: It is a demandable return for long-term having a discount in comparison to the short-term reward.

  • Value Function: It specifies the total amount of rewards or the value of the states. It is an agent to initiate from that state.

  • Model of the environment: To imitates the behavior of the environment and helps in making inferences or insights, a model of the environment is required. It also determines how the environment will behave.

  • Model-based methods: It is a mode of various methods in order to solve reinforcement learning problems.

  • Q value or action value: Q value is almost similar to value but only has a difference as it takes current action as an extra parameter.


Further added, there are two types of Reinforcement learning; 


Positive Reinforcement learning, when an episode of actions occurs due to a particular behavior that enhances the power and number of frequencies of the behavior so that it has a positive effect on behavior.


It maximizes the efficiency and performance of the state and also nurtures changes in the long run. But sometimes, an excess amount of rewards could lead to giving burden on states which can decrease the results.



Negative Reinforcement Learning, when a negative condition can be avoided or stopped to strengthen the behavior in order to get an appropriate reward. It increases behavior and gives resistance up to a minimum parameter of performance. It only stores the minimum behavior to meet the requirements.


Along with more advanced features and technologies, there is always some pitfalls with all methods, the same in the case of reinforcement learning, you must find designed rewards or even features awarded are much involved in its process, even the various numbers of parameters might affect the learning speed of an agent.


Depending upon the nature of the environment, observability may vary either completely or partially, like, the realistic environment can be non-stationary and have partial observability.



Characteristics and Application of Reinforcement learning


When you need to understand which situation needs an action when you want to explore which action produces the maximum amount of rewards for a long period of time, you probably required the reinforcement learning method. Also in order to get the leaning agent along with reward function and to estimate possible procedure or method when you want to obtain the largest reward, reinforcement learning plays a crucial role.


With these numbers of specialties, reinforcement learning exhibits the following characteristics;


  • Excluded with supervisor, and possess only a real number or reward signal

  • Appropriate decision making in sequential order

  • Rewards for each and every time of action in reinforcement problems

  • Delayed feedback for actions

  • To determine succeeding data by agent’s actions


Reinforcement learning has a wide range of applications based on rewards or experience of actions;


  • Robotics for industrial automation,

  • Machine learning and data processing

  • Creating the training systems for custom instruction

  • Different aspects of materials for the requirement of students

  • Planning and making strategies for businesses

  • Controlling aircraft and robotic motion 



Let’s learn how Reinforcement Learning differs from Supervised Learning?


  • In supervised learning, the training dataset has its own answer key so that when the model gets trained including certain sets of correct answers, in the opposite of that without having a training dataset, reinforcement agent decides what and how to perform for a given task to get a reward or experience. 


  • In supervised learning, a decision is made on the basis of the input provided at the beginning, whereas reinforcement learning gives ample ways to make decisions sequentially. 


  • Supervised learning consistently works on the given sample data or examples under a given dataset, opposite to that reinforcement learning first makes interactions with the environment then does work accordingly.


  • Every decision making is independent of each other in supervised learning so that labels are provided for each decision, in contrast to that, in reinforcement learning every decision is dependent on other entities, in accordance with that labels are designed to all the dependent decisions.


The cartoon image is showing the two different machine learning algorithms: supervised learning and reinforcement learning. Both learning methods have some common differences.

Supervised learning and reinforcement learning are different



  • You mostly find that supervised learning starts operating with an interactive software system or application whereas reinforcement learning relies on AI, it supports and works with AI-based models where human interaction is usual.





Components of Reinforcement Learning


Reinforcement learning has the main agent and environment as the main element, but it also has other four subcomponents;


Policy: It is a kind of depicting from the recognized state of the environment to steps to be taken place in those states. The policy is not less than the nucleus for reinforcement learning agents, it is alone enough to determine behavior. There might be stochastic, defining random probabilities for individual action.


Rewards: At the time of each and every step, the environment sends a single reward to the reinforcement learning agent. The agent’s only aim is to maximize the total reward it holds in the deep field. What could be possibly good or bad signals for the agent are decided by the number of rewards obtained. It may be a stochastic function of the state and action.


Value Function: It specifies the utility of the state, i.e. starting from the current state, the total quantity of reward expecting by an agent to acquire up to the future. As rewards fix the direct and fundamental advantage of the environmental states, values show the long-run advantages of states following the states that are likely to support and the rewards available in those states.


For example, a state tries to produce a low instant reward and still has a high core value because it is constantly succeeded by other states that also produce high rewards or vice versa.


Model of the Environment: It ensures the behavior of the environment that further permits insights to be executed regarding how the environment will behave. For example, given a state and an action, the existing model predicts the next resultant state and the next reward based on the model consequences. Model-based methods are preferred for solving reinforcement learning problems[1].





Hopefully, you enjoyed reading this blog, I have presented you the basic concept of reinforcement learning and its working element. Today, reinforcement has become an amazing field to explore and learn. Major development had been made in this field and many more yet to come. This blog covered the mechanism and working theory of reinforcement learning. The basic intro for the characteristics and application also covered during writing the blog.


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