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Difference Between Random Forest and Decision Tree in Machine Learning

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decision tree vs random forest

Brief Introduction Regarding Machine Learning Algorithms.

Algorithms play a critical role in executing any computer program effectively. The faster an algorithm operates, the quicker the program will execute. Machine learning offers various algorithms for regression and classification tasks, but two of the most widely used ones are decision trees and random forests. Although these algorithms have similarities, they also have differences that set them apart. This blog post will examine the distinctions between decision trees and random forests.

What is a Decision Tree Algorithm?

decision tree algorithm

Early artificial intelligence pioneer Arthur Samuel introduced Decision Trees in the 1950s. These trees are closely associated with game theory and were created to address decision-making challenges in the military strategy and economics domains.

The Decision Tree algorithm is a widely-used supervised learning technique in machine learning for classification and regression tasks. The algorithm repeatedly divides the dataset into smaller subsets based on the most informative feature to increase class separation or minimize variance. Each split results in a new branch in the tree, and the outcome is a tree structure where each leaf node represents a class or a value.

What advantages of the Decision Tree Algorithm?

Decision trees have the advantages of being interpretable, handling both categorical and continuous data, and working for binary and multi-class classification and regression tasks. However, overfitting can be a problem, especially if the tree is too deep, leading to a poor generalization of new data.


Let’s go through an easy example.

To use a decision tree to decide whether to run based on the weather and energy level, you would start by creating a root node labeled “Should I go for a run?” The first decision point would be based on the weather, with a branch for “Is it raining?” If it is raining, the decision would be not to go for a run. If it’s not raining, move to the next decision point based on an energy level with a branch for “Am I feeling energetic?” If you are feeling energetic, the decision would be to go for a run, and if not, the decision would be not to go for a run. The decision tree helps by considering weather and energy levels, with a clear set of conditions for each outcome.

decision tree node representation

What is a Random Forest Algorithm?

random forest algorithm

In the early 2000s, Leo Breiman, a notable figure in machine learning, introduced the concept of Random Forests. Breiman was a pioneer in the field of machine learning.

Random Forest is an ensemble machine-learning algorithm that can be used for classification, regression, and other tasks. It combines multiple decision trees to form a forest, each trained on a random subset of the training data and a random subset of input features. During training, each tree learns to make predictions based on the features of the data points it sees. During prediction, each tree makes a prediction, and the final result is an average of individual tree predictions for regression or the majority vote for classification

Advantages of Random Forest Algorithm.

Random Forest offers several benefits over decision trees, such as improved Accuracy, reduced overfitting, and better performance on high-dimensional data. It is scalable and suitable for large datasets with many input features. Random Forest is commonly used in finance, marketing, and healthcare, among other fields, and is among the most popular machine learning algorithms.


Let’s understand by an Example.

To better understand how the random forest algorithm works, consider an example where you plan to buy a new cycle. You have multiple options, such as cycles X, Y, and Z. To make an informed decision, you could build a separate decision tree for each cycle option and then combine the results to determine the best option overall. This approach involves building separate decision trees for each cycle option, similar to building a single decision tree, and then analyzing the output from each tree using a predictive system to find the best cycle option. Using a random forest algorithm, you can apply this approach across many options or scenarios to make more accurate and informed decisions.

Difference between Decision Tree and Random Forest in Machine Learning:-

  • Based on Speed:-Decision Trees are generally faster than Random Forests in Machine Learning. It is because Decision Trees are simpler models that require less computational resources to build and make predictions.
  • Based on Interpretation:-Decision Trees are relatively easy to interpret, making them useful for exploratory data analysis and for building simple models. On the other hand, Random Forests are more difficult to interpret than Decision Trees. It is because Random Forests are ensemble models that combine multiple Decision Trees, making it more challenging to understand how the model is making predictions.
  • Based on Time:- Decision Tree takes less Time because they only involve creating a single tree. Random forests, however, require creating multiple decision trees, which takes more Time. 
  • Based on Linear Problems:-Decision Tree is best to build a solution for a linear data pattern; on the other hand, Random Forest cannot handle data with a linear pattern. In other words, if the data has a linear structure, it is better to use a Decision Tree to build a solution than a Random Forest.
  • Based on Overfitting:-In the case of the Decision Tree, there is a possibility of overfitting data; on the other hand, there is a reduced risk of overfitting because of multiple trees.
  • Based on Computation:-   Decision Tree is a straightforward algorithm that is relatively easy to comprehend and doesn’t require much computational power to create and use. However, the computational complexity of a Random Forest is higher than that of a single Decision Tree since it needs to build several trees and average their predictions.
  • Based on Visualization:-Visualization in Decision Tree is easy but quite complex in the case of Random forest. A Decision Tree can be visualized as a single tree structure showing the hierarchy of features used to make decisions. A Random Forest can be visualized as a combination of multiple trees.
  • Based on Outliers:-Decision trees are highly Prone to be affected by outliers, whereas the Random forest is much less likely to be affected by outliers.
  • Based on Implementation:-Decision Trees are rapid model building as it fits the dataset quickly, whereas, in the case of Random Forest, it’s slow to build the model depending on the size of the dataset. 
  • Based on Accuracy:- Decision Tree gives less accurate results, whereas Random forest gives more accurate results. In terms of Accuracy, random forests generally perform better than decision trees, especially on complex datasets with many features. They can capture more complex relationships between the features and the target variable.

What choice to make between the Decision Tree and Random Forest?

The decision to use either a decision tree or a random forest depends on the specific problem and its requirements. If speed is important and Accuracy is not a top priority, a decision tree may be a good choice since it can be quickly built. However, if Accuracy is important and Time is not a constraint, a random forest may be preferred since it can produce better predictions but requires more Time for training. Decision trees are better suited for larger datasets as they are faster, while random forests require more training time for larger datasets. Ultimately, the choice between the two models should be based on the specific problem and its requirements.

The Conclusion

After considering the strengths and weaknesses of each algorithm, it is important to analyze the problem and choose the most suitable algorithm. We can make a more informed decision by understanding the differences between decision trees and random forest algorithms. Implementing these algorithms in practice is recommended to gain a deeper understanding of these topics.

Frequently Asked Question and Answer

What is decision tree and random forest in machine learning?
In Machine Learning, Decision tree and random forest are machine learning algorithms used for classification and regression tasks. A decision tree is a structure where internal nodes represent a test on an attribute, branches represent the outcome of the test, and leaves represent a class label or continuous value.
What is the main reason to use a random forest versus a
decision tree?
The main benefit of switching from a decision tree to a random forest algorithm is to increase the model's accuracy and stability, particularly for larger and more complex datasets. Despite being straightforward and simple to grasp, decision trees are prone to overfitting, leading to poor performance on new data. Random forest, in contrast, reduces overfitting and boosts diversity by employing numerous decision trees that have been trained on various subsets of data and features.
Is random forest a decision tree algorithm?
Decision tree and random forest are two closely linked but different machine learning algorithms. A decision tree is a straightforward tree-like structure used for classification and regression tasks. Each node in the tree reflects a decision based on a set of features, and the leaf nodes are where the ultimate prediction is made. On the other hand, random forest is an ensemble learning technique that uses various decision trees to increase the model's stability and accuracy.
Why random forest is better than decision tree?
Because it addresses the shortcomings of the decision tree algorithm, random forest is considered better than a single decision tree. Furthermore, by combining numerous decision trees that have been trained on various subsets of data and features, random forest minimises overfitting and creates a more robust and general model.
What is the purpose of a decision tree?
Using input features, a decision tree is a machine-learning algorithm used to forecast the value of a goal variable. It can be applied to classification and regression problems, and it generates a tree-like structure where each node reflects a choice based on the value of a feature. The algorithm recursively selects the feature to divide the data into two subsets that offer the most information gain to construct a decision tree. This procedure is repeated until all of the data in each branch is of the same class or has the same value for the target variable.
What is decision tree?
A machine learning algorithm known as a decision tree, which is based on a tree-like structure where each node reflects a decision made using a feature, is used for regression and classification issues. The algorithm divides the data recursively based on the feature that yields the most information gain, starting with the complete dataset at the root node, and continues until each branch has the same class or value for the target variable.