Random Forest Algorithm in Machine Learning

Last Updated: 15th December, 2023

Random Forest is a type of supervised machine learning algorithm based on ensemble learning. It is a collection of decision trees, where each tree is trained using a randomly selected subset of the data. The random forest algorithm combines multiple decision trees in order to reduce the risk of overfitting. The result is a much more accurate and stable prediction. It is one of the most popular and widely used machine learning algorithms. It can be used for both regression and classification tasks. It is also used for feature selection and to identify important variables in a dataset. It is an efficient and effective tool for complex data analysis.

What is Random Forest Algorithm?

Random Forest is a well-known machine learning algorithm from the supervised learning approach. It may be applied to both classification and regression issues in machine learning. It is built on the notion of ensemble learning, which is a method that involves integrating several classifiers to solve a complicated issue and enhance the model's performance.

"Random Forest is a classifier that comprises a number of decision trees on various subsets of the provided dataset and takes the average to enhance the predicted accuracy of that dataset," as the name implies. Instead of depending on a single decision tree, the random forest collects the predictions from each tree and predicts the final output based on the majority vote of predictions.

Random Forest Prediction

Assumptions for Random Forest

Because the random forest mixes numerous trees to predict the dataset's class, some decision trees may predict the proper output while others may not. But, when all of the trees are combined, they predict the proper outcome. As a result, the following are two assumptions for a better Random forest classifier:

• There should be some real values in the dataset's feature variable so that the classifier can predict correct outcomes rather than guesses.
• Each tree's predictions must have very low correlations.

Why use Random Forest?

Here are some reasons why we should utilise the Random Forest algorithm:

• It requires shorter training time than other algorithms.
• It predicts output with great accuracy, and it works efficiently even on big datasets.
• It can also retain accuracy when a significant amount of data is absent.

How does the Random Forest Algorithm Work?

Random Forest operates in two stages: the first is to generate the random forest by mixing N decision trees, and the second is to make predictions for each tree generated in the first phase.

Step 1: Choose K data points at random from the training set.

Step 2: Create decision trees for the specified data points (Subsets).

Step 3: Determine the number N for the number of decision trees you wish to construct.

Step 4: Repeat Steps 1 and 2.

Step 5: Find the predictions of each decision tree for new data points and assign the new data points to the category with the most votes.

The following random forest algorithm example will help you understand how the algorithm works:

Assume there is a dataset containing several fruit photos. As a result, the Random forest classifier is given this dataset. The dataset is subdivided and distributed to each decision tree. During the training phase, each decision tree gives a prediction result, and when a new data point occurs, the Random Forest classifier predicts the final choice based on the majority of outcomes. Consider the following image:

Random Forest Algorithm

Applications of Random Forest

1. Credit Card Fraud Detection: Random Forest has been used to detect fraudulent credit card transactions. It can identify outliers and detect fraudulent activities by analyzing a variety of features such as amount, type of transaction, location etc.
2. Stock Market Prediction: Random Forest has been used to predict the stock market prices. It can identify patterns in the data and make predictions about future prices.
3. Image Recognition: Random Forest has been used in image recognition. It can be used to classify objects in images and identify patterns in the data.
4. Customer Churn Prediction: Random Forest has been used to predict customer churn. It can analyze customer data and predict the likelihood of a customer to leave the company.
5. Diabetes Prediction: Random Forest has been used to predict the onset of diabetes. It can analyze a variety of features such as age, lifestyle, diet and medical history to predict the risk of developing diabetes.

Advantages and Disadvantages of Random Forest

Advantages of Random Forest

1. Random forests are highly accurate and powerful. They can handle large amounts of data and are robust to outliers.
2. Random forests are easy to use, interpret and visualize.
3. The training time of a random forest is fast compared to many other techniques.
4. They are resistant to overfitting and can be used to estimate missing data.
5. The algorithm is versatile and can be used for both classification and regression tasks.

Disadvantages of Random Forest

1. Random forests are prone to overfitting if the data contains a large number of features.
2. Random forests are very slow in making predictions when compared to other algorithms.
3. They are not suitable for real-time applications as they require the entire dataset to be stored in memory.
4. They require a lot of hyperparameters to be tuned for optimal performance.
5. Random forests are not good for tasks that require precise predictions as they are only able to provide an estimate of the outcome.

Python Implementation of Random Forest Algorithm

Random forest algorithm is a supervised learning algorithm for classification and regression problem. It is an ensemble learning method which combines the prediction of multiple decision trees to determine the final output of the algorithm. It works by creating a forest of decision trees from randomly selected subset of training set. Each tree is grown to the largest extent possible and there is no pruning. The prediction of the individual trees are combined to determine the final output of the algorithm.

The main steps involved in the random forest algorithm are as follows:

1. Select random samples from the dataset.
2. Build decision trees using the samples.
3. Make predictions using each tree.
4. Combine the predictions to get the final output.

The random forest algorithm is an efficient and powerful machine learning technique that can be used for both classification and regression tasks. It is easy to implement and can be used to solve complex problems. It is also robust to outliers, missing values, and can handle large datasets.

Lets take the following dataset for demo:

Link: https://www.kaggle.com/code/sandragracenelson/logistic-regression-on-user-data-csv

Implementation

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The above code is used to implement the Random Forest algorithm in Python. It begins by importing the necessary libraries such as Pandas, Numpy and the Random Forest Classifier from the sklearn library. Then the dataset is read into a Pandas DataFrame and the features and target are separated into two separate variables (X and y). Next, a Random Forest Classifier model is created and trained using the X and y variables. Finally, the model is used to predict the target variable using the features.

Conclusion

Random forest is an effective machine learning algorithm that can be used to build powerful models for a variety of tasks. It is a highly accurate and robust method that can handle high-dimensional data and large-scale datasets. It is also capable of handling missing values and outliers, so it is suitable for a variety of real-world applications. With its ability to generate accurate predictions, random forest is a popular choice for many data science tasks.

Key Takeaways on Random Forest Algorithm

1. Random forest is an ensemble technique that uses multiple decision trees to make predictions.
2. It is effective in dealing with high-dimensional data and is also a robust algorithm, meaning it can handle missing or corrupted data points.
3. It is effective at reducing variance in model predictions, which can help improve accuracy and avoid overfitting.
4. Random forest is a fast and efficient algorithm, meaning it can process large datasets quickly and can be used for both classification and regression tasks.
5. It is important to tune the hyperparameters of a random forest model in order to optimize its performance.

Quiz

1.What is the main goal of using a Random Forest algorithm? 

1. To classify data 
2. To reduce variance 
3. To reduce bias 
4.  To predict outcomes

Answer: d. To predict outcomes

2. What is the main difference between a Decision Tree and a Random Forest? 

1. Random Forest is more accurate
2.  Decision Tree is more accurate
3.  Random Forest creates multiple Decision Trees 
4.  Decision Tree creates multiple Random Forest

Answer: c. Random Forest creates multiple Decision Trees

3.What is the benefit of using a Random Forest algorithm over a single Decision Tree? 

1. It reduces variance 
2. It reduces bias 
3. It is more accurate 
4.  It is faster

Answer: c. It is more accurate

4.What is the main advantage of using Random Forest over other algorithms? 

1.  It is more accurate 
2.  It is faster 
3.  It is easy to use 
4. It can handle large datasets

Answer: d. It can handle large datasets