Classification vs. Regression in Machine Learning: What’s the Difference?

Classification and regression are two of the most popular techniques in machine learning, each tailored to specific problem types. Both methods fall under supervised learning, meaning the machine learning algorithms use labeled training data to learn and apply patterns in the data to unseen information. Classification sorts data into predefined categories, while regression predicts continuous outcome values. Understanding each method's advantages and disadvantages and how they compare can help you choose the right method for your workflow. 

What is classification in machine learning?

Classification in machine learning categorizes data into predefined groups based on shared characteristics. Machine learning models learn the characteristics of each group from the input data and then generalize this information to new data points. You’d likely choose this for tasks where your output falls into a category, meaning it’s a discrete outcome. For example, you might determine the type of tumor from a medical scan, segment customers based on purchasing behavior, categorize customer feedback, or classify email types.

What is classification used for?

The application of classification depends on the type of classification algorithm you use. You can opt for different classification models, such as binary, multiclass, and multilabel. 

Binary classification categorizes data into one of two groups. Examples of this might include filtering spam emails (spam/not spam), detecting fraud (fraud/not fraud), or diagnosing a disease (disease/no disease).

Multiclass classification groups data into several distinctive groups with no overlap. For example, if you had an image classifier, you might group pictures of dogs into breeds such as “dalmatian,” “collie,” and “poodle.” If you have overlap in your groups, this is a multilabel classification. For example, if you classified videos, you could simultaneously label a movie as “action” or “comedy” or label it as both genres. 

Advantages and disadvantages of classification

To determine whether classification is the right machine learning method for your data, it’s important to weigh the pros and cons to make an informed decision. Advantages and disadvantages to consider as a starting point include:

Advantages

• Versatile input data: You can use classification with various input styles, including text, images, audio, or video.

• Easily evaluated: You can evaluate the performance of your model with many established indicators and toolkits, helping you make decisions to maximize efficiency, speed, and quality.

• Can make discrete or continuous predictions: You can use classification to make discrete predictions, such as “disease” or “no disease,” as well as continuous predictions, such as “25 percent probability of disease” and “75 percent probability of no disease.” 

Disadvantages

• Risk of overfitting or underfitting: Without sufficient training data, your model may “overfit” by aligning too closely with the training data and failing to generalize to new data. Conversely, it could “underfit” by struggling to learn meaningful patterns due to insufficient exposure.

• Requires high-level training data: Your training data set must be structured in an appropriate format to learn the categories and attribute features to them. This involves some pre-processing and data management.

What is regression in machine learning?

Regression in machine learning is a technique used to predict a continuous outcome value using the value of input variables. The algorithm analyzes the input data to understand the relationship between independent variables and the dependent variable. For example, to predict a student's future exam score (a continuous variable), you might use study time, sleep hours, and previous grade averages as input variables. Regression models establish a consistent framework for making accurate predictions of the dependent variable by identifying patterns and relationships in the data.

What is regression used for?

Similar to classification methods, the application of regression depends on the type of regression used. Often, you will work with simple linear regression or multiple linear regression. 

Simple linear regression models how independent variables relate to a dependent variable by finding a straight line that best fits the data. For example, you might predict housing prices based on square footage, product sales based on marketing budget, or disease spread based on vaccination rates. 

With multiple linear regression, you add more independent variables to predict your response variable value. For example, you might predict housing prices based on square footage, zip code, and number of available houses. 

Advantages and disadvantages of regression

Regression is a powerful tool when used under the right conditions but has limitations. Considering the advantages and disadvantages can help you make an educated choice between regression and other machine learning methods.

Advantages

• Handles continuous and categorical outputs: Linear regression allows you to handle continuous outputs, while logistic regression works well with categorical outputs.

• Easily interpretable: Regression outputs offer insight into the magnitude of the association between variables, allowing a clearer understanding of your model.

• Low computational requirement: Regression analysis is simpler and more efficient to implement compared to other machine learning algorithms.

Disadvantages

• Relies on accurate data and assumptions: If you have incorrect data or assumptions, regression models can make inaccurate predictions, leading to poor decision-making.

• Doesn’t imply causation: While regression results can show correlations between variables, they do not necessarily imply that changes in certain variables cause changes in another.

• Requires careful variable selection: Accurate predictions for the dependent variable rely on selecting the right set of independent variables to effectively capture the underlying relationships in the data. 

Tying it together: Classification vs. regression

Classification and regression are two powerful tools in machine learning, each designed for distinct use cases. Classification algorithms sort input data into groups, such as classifying a child’s height as “tall” or “not tall.” These models are ideal for tasks with clear, discrete outcomes.

On the other hand, regression models use several input variables to predict a continuous numerical value for the response variable, such as estimating a child’s exact height based on age and gender. While many use cases are distinct, some areas may have overlap. For example, logistic regression—despite its name—is a classification method that predicts the likelihood of an outcome falling into one of several categories. For example, you could use logistic regression to classify lung disease status (e.g., “disease” or “no disease”) based on predictors like age, weight, smoking history, and family medical history. Understanding when to use classification and regression allows you to effectively address various predictive tasks, from simple grouping to complex prediction models.

Learn more about machine learning on Coursera

Classification and regression are two popular machine learning techniques allowing you to group data and predict your outcome variable. You can continue learning about machine learning by taking compelling courses and Professional Certificates on Coursera.

For an introduction to artificial intelligence (AI), consider taking the Generative AI for Everyone course offered by DeepLearning.AI. If you want a broader introduction to statistical methods, the Meta Data Analyst Professional Certificate offers a five-course series over a broad range of data analytics methods.