# What is Binary classification?

by Stephen M. Walker II, Co-Founder / CEO

## What is Binary Classification?

Binary classification is a type of supervised learning algorithm in machine learning that categorizes new observations into one of two classes. It's a fundamental task in machine learning where the goal is to predict which of two possible classes an instance of data belongs to. The output of binary classification is a binary outcome, where the result can either be positive or negative, often represented as 1 or 0, true or false, yes or no, etc.

Binary classification has a wide range of applications across various fields. For instance, in medical diagnosis, it can be used to determine whether a patient is healthy or diseased. In email analysis, it can be used to classify emails as spam or not spam. In financial data analysis, it can be used to identify fraudulent transactions. In marketing, it can be used to predict whether a website visitor will make a purchase or not.

There are several algorithms used for binary classification, including but not limited to:

• Logistic Regression
• Decision Trees
• Random Forests
• Support Vector Machines
• Neural Networks
• Bayesian Networks
• K-Nearest Neighbors
• Naive Bayes

Each of these algorithms has its strengths and weaknesses, and their performance can vary depending on the specific characteristics of the data set, such as the number of observations, the dimensionality of the feature vector, and the balance of classes.

In Python, libraries like scikit-learn provide easy-to-use interfaces for implementing these algorithms. For example, the breast cancer dataset from scikit-learn can be used to demonstrate binary classification in a logistic regression model.

It's important to note that in many practical binary classification problems, the two groups are not symmetric, and the relative proportion of different types of errors can be of interest. For example, in medical testing, detecting a disease when it is not present (a false positive) is considered differently from not detecting a disease when it is present (a false negative).

## What are some common applications of binary classification?

Binary classification is a fundamental task in machine learning where the goal is to categorize elements into one of two groups. Here are some common applications of binary classification:

1. Medical Diagnosis — Binary classification is often used in the medical field to determine if a patient has a certain disease or not. For example, a binary classifier could take a patient's symptoms as input features and output a diagnosis as positive or negative for a specific disease.

2. Email Spam Detection — In the realm of information retrieval, binary classification is used to filter spam emails. Emails are classified into two categories: "spam" and "not spam".

3. Financial Risk Assessment — In finance, binary classification can be used to assess credit risk. For instance, customers can be classified into "high risk" and "low risk" categories based on their credit history and other financial data.

4. Quality Control in Industry — Binary classification can be used in quality control processes to decide whether a product meets a certain specification or not.

5. Marketing — In marketing, customers can be classified into "buyers" and "non-buyers" or "prefers brand A" versus "prefers brand B" based on their purchasing behavior and preferences.

6. Retail — Binary classification can be used to decide whether certain products meet the selection criteria or not, helping retailers refine their product assortment.

7. Image Classification — Binary classification can be used in image classification tasks, such as determining whether an image contains a specific object or not.

These applications utilize various binary classification methods such as decision trees, random forests, Bayesian networks, support vector machines, neural networks, and logistic regression. The choice of method depends on the specific problem, the nature of the data, and the performance requirements.

## More terms

### What is an echo state network?

An Echo State Network (ESN) is a type of recurrent neural network (RNN) that falls under the umbrella of reservoir computing. It is characterized by a sparsely connected hidden layer, often referred to as the "reservoir", where the connectivity and weights of the neurons are fixed and randomly assigned.

### What is Receiver Operating Characteristic Area Under Curve (ROC-AUC)?

ROC-AUC, or Receiver Operating Characteristic Area Under Curve, is a performance measurement for classification problems in machine learning. The ROC curve is a graphical representation that illustrates the performance of a binary classifier model at varying threshold values. It plots the true positive rate (TPR) against the false positive rate (FPR) at different classification thresholds.