What is Reinforcement Learning in Machine Learning? Easy Guide

What is Reinforcement Learning in Machine Learning?

Do you want to know What is Reinforcement Learning in Machine Learning??… If yes, this blog is for you. In this blog, I will explain What is Reinforcement Learning in Machine Learning using examples.

What is Reinforcement Learning in Machine Learning?

What is Reinforcement Learning?

Let’s start with a fun scenario: teaching a computer to master a task without giving it step-by-step instructions. Instead, we let it learn by trying things out, making mistakes, and getting better over time. This is what Reinforcement Learning is all about. It’s like how you learn a new game or skill by practice. So, let’s dig in!

The Core of Reinforcement Learning

At the heart of RL is the “agent.” Think of the agent as a smart piece of software that wants to become really good at something.

Meet the Agent: But here’s the twist; the agent doesn’t work in isolation. It interacts with an “environment.” This environment is like the setting or context in which the agent operates, whether it’s a game world or a real-life situation.

Chasing Rewards: What’s the agent’s goal? To collect “rewards.” These rewards are like virtual gold stars or points that the agent earns when it does something right in the environment.

Check-> Become a Deep Reinforcement Learning Expert 

How Reinforcement Learning Works

To grasp RL fully, let’s peek behind the curtain and see how it operates:

Exploration vs. Exploitation: Imagine you’re playing a game. Sometimes, you try new strategies (exploration), and other times, you stick with what you know works (exploitation). This balance is a crucial part of RL.

Markov Decision Process (MDP): This may sound complex, but it’s like having a roadmap to help the agent decide what to do next based on its current situation in the environment.

Policies and Values: “Policies” are like game plans that tell the agent what to do in different situations. “Values” are like scores that help the agent understand how good or bad a situation is.

Key Terms

To navigate RL smoothly, let’s get familiar with some key terms:

States: States are like snapshots of what’s happening in the environment at a given moment. Think of it as pausing a video game to see where you are; that’s a state.

Actions: Actions are the choices the agent can make. It could be moving a character in a game, investing in stocks, or anything relevant to the task.

Rewards: Rewards are like feedback or prizes. They tell the agent if it’s doing well (positive rewards) or not (negative rewards).

Varieties of RL

RL isn’t one-size-fits-all. There are different types, each with its unique approach to teaching the agent:

Q-Learning: Think of this as the agent keeping a list of good actions for different situations. It uses this list to make better choices over time.

Deep Q-Networks (DQN): In DQN, our agent uses powerful computers and math to remember which actions are good, especially when things get complex, like recognizing images.

Policy Gradient Methods: Instead of lists, this approach directly teaches the agent what to do in various situations, like learning to cook without recipes.

Proximal Policy Optimization (PPO): PPO finds a balance between trying new actions and sticking to what’s already proven to work.

Q-Learning Example

Let’s see how Q-Learning works with a simple example of a robot finding its way through a maze.

Setting Up the Q-Table

We start with something called a Q-Table. It’s like a cheat sheet for the robot. It helps the robot make choices. The table has rows and columns. Rows are for where the robot is in the maze, and columns are for what actions it can take (like going up, down, left, or right).

| Where the Robot Is | Up | Down | Left | Right |
| (0,0)              | ?  |  ?   |  ?   |   ?   |
| (0,1)              | ?  |  ?   |  ?   |   ?   |
| ...                | ...|  ... |  ... |  ...  |
| (N,M)              | ?  |  ?   |  ?   |   ?   |

At the start, all the boxes in the table have question marks because the robot doesn’t know what to do yet.

Robot’s Exploration and Learning

Now, our robot begins to explore the maze. It decides which way to move, like up or down. Then, it gets a reward based on what happens. If it gets closer to the exit, it gets a good reward. If it hits a wall, it gets a bad reward.

Here’s how Q-Learning helps:

  • The robot takes an action, says “Up,” and moves to a new spot in the maze.
  • It checks the Q-Table for that spot-action pair (for example, (0,0) – Up).
  • The Q-value gets updated using a formula:
Q(state, action) = (1 - learning_rate) * Q(state, action) + learning_rate * (reward + discount_rate * max(Q(new_state, all_actions)))
  • learning_rate: This is how much the robot learns from each experience. It’s like deciding how much attention to pay to new stuff.
  • discount_rate: This helps the robot think about future rewards. A bigger value makes the robot think more about the long term.
  • max(Q(new_state, all_actions)): This part encourages the robot to pick actions with the highest Q-Values in the new spot. It’s like the robot saying, “I’m going to do what I think works best.”

Learning Again and Again

The robot does this again and again, exploring, moving, and updating its Q-Values. It does this until it either reaches the exit or finishes a certain number of moves. Over time, the Q-Table gets filled with good values, and the robot gets better at finding its way.

Using What It Learned

Once the Q-Table has good values, the robot stops guessing and starts using the Q-Table to make smart moves. It’s like the robot has learned the best path through the maze and doesn’t need to guess anymore.

Q-Learning is like teaching a robot to learn from its adventures and make clever choices to reach its goal. It’s not just for mazes; it can help robots and computers make smart decisions in all sorts of situations where learning from experience is handy.

Check-> Deep Learning and Reinforcement Learning

Reinforcement Learning Example

Imagine teaching a robot to explore a maze. In the beginning, it knows nothing. But as it moves around and gets closer to the exit, it gets rewards. Over time, it figures out the best path, all while juggling the exploration of new routes and using what it’s learned.

Why is it Called Reinforcement Learning?

The name “reinforcement” comes from psychology. It refers to learning through rewards and punishments. In RL, the agent gets “reinforced” with rewards when it makes good choices, just like we reinforce good behavior in kids with rewards.

What’s the Difference Between Deep Learning and Reinforcement Learning?

Deep Learning focuses on training computers to recognize patterns in data, like identifying cats in pictures. RL, on the other hand, is about making decisions over time, where an agent learns to interact with its environment to maximize rewards.

How Does Reinforcement Learning Differ from Supervised Learning?

There are two main differences:

  1. Learning Paradigm:
    • In Supervised Learning, the computer is trained on labeled data with clear answers.
    • In Reinforcement Learning, the computer learns by trying things out and getting rewards for good actions.
  2. Objective:
    • Supervised Learning aims to make accurate predictions or classifications.
    • Reinforcement Learning aims to learn a strategy (policy) that maximizes cumulative rewards over time.


Reinforcement Learning is like teaching a computer to learn from experience, just like we do when we practice and improve at a game or skill. It holds great potential to transform various fields, but it also requires a delicate balance between exploring new options and sticking to what works. As RL continues to evolve, we can look forward to exciting advancements and a future enriched by intelligent, learning computers.

I hope now you understand What is Reinforcement Learning in Machine Learning.

Happy Learning!

Thank YOU!

Though of the Day…

Anyone who stops learning is old, whether at twenty or eighty. Anyone who keeps learning stays young.

– Henry Ford

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Written By Aqsa Zafar

Founder of MLTUT, Machine Learning Ph.D. scholar at Dayananda Sagar University. Research on social media depression detection. Create tutorials on ML and data science for diverse applications. Passionate about sharing knowledge through website and social media.

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