Machine learning is an artificial intelligence technique that allows systems to learn and improve automatically based on data, without being explicitly programmed. It is based on the idea that systems can learn autonomously from data, without needing to be explicitly programmed to perform a specific task.
To implement a machine learning model, it is necessary to collect and prepare the data, choose and train a model, evaluate and adjust the performance of the model, and finally deploy it into a system. The choice and adjustment of the model is an iterative process, where it is necessary to experiment with different techniques and parameters to find the best solution for the specific problem.
In summary, machine learning is an artificial intelligence technique that allows systems to learn and improve automatically based on data, without being explicitly programmed. It is composed of different types of learning and techniques, and is applicable to a variety of problems, from prediction and classification to decision-making and process automation.
There are three main types of machine learning:
- Supervised learning;
- Unsupervised learning;
- Reinforcement learning.
Supervised Learning
Supervised learning is when the machine learning model is trained with labeled data, where the expected response is known. This is commonly used for classification and regression, where the goal is to predict an output from inputs.
For example, a supervised learning model can be trained with thousands of labeled images of cats and dogs, and then be able to classify new images as cats or dogs with high accuracy. The model learns from labeled examples, which are used to train the model and make predictions about new, unseen examples.
This is the most common type of machine learning and it’s widely used in many applications such as image recognition, speech recognition, natural language processing and more.
Unsupervised Learning
Unsupervised learning is a type of machine learning where the model is trained on unlabeled data, where the expected output is not known. This is commonly used for clustering and dimensionality reduction, where the goal is to find patterns and relationships in the data. For example, an unsupervised learning model can be used to group customers with similar characteristics, such as:
- Age;
- Income;
- Location.
There is no need of having a specific output to predict. The model must discover the underlying structure or patterns in the data on its own.
Reinforcement Learning
Reinforcement learning is when the machine learning model is trained with positive or negative feedback, in order to improve its performance over time. This is commonly used in decision-making systems, where the goal is to take actions that maximize a reward over time.
For example, a reinforcement learning model can be used to control an autonomous car, making decisions based on sensors and feedback from the current road situation, with the goal of maximizing safety and efficiency of the trip.
Other Machine Learning Techniques
In addition, there are various machine learning techniques, such as neural networks, decision trees, random forests, gradient boosting, among others. Each technique has its own advantages and disadvantages and is applicable to different types of problems.
- Neural Networks:
Neural networks are a technique of machine learning inspired by the biological structure of the human brain. They consist of several layers of nodes or neurons, each connected to another. These neurons are responsible for processing and transmitting information between layers. There are several types of neural networks, such as perceptrons, feedforward neural networks, recurrent neural networks and deep neural networks.
Feedforward neural networks are the simplest and most common. They consist of an input layer, one or more hidden layers and an output layer. The input layer is where the input data is provided, the hidden layers process this data and the output layer provides the final output.
Recurrent neural networks are used when the data has a temporal sequence. They have an internal memory and are able to process input sequences of multiple steps.
Deep neural networks, also known as deep learning neural networks, consist of many hidden layers and are able to learn hierarchical representations of data. They are used in applications such as image recognition, natural language processing, and text generation.
Neural networks are trained using supervised learning algorithms, where a labeled training dataset is used to adjust the weights of the neurons in the network. They are highly flexible and can be used to solve a variety of problems, such as classification, regression, text generation and much more.
- Decision Trees:
Decision trees are a supervised machine learning technique that allows for predictions based on input features. They work by creating a tree structure where each node represents a decision to be made based on an input feature, and each branch represents a possible response to that decision. The leaf of a tree represents the final prediction.
To build a decision tree, recursive partitioning techniques are used, where the tree is built from the root and is divided into sub-trees until the leaves represent subsets of data with similar features. The decision tree is constructed using a measure of impurity, such as entropy or Gini, to measure the quality of a split. This helps to choose the best feature to divide the data.
This technique is widely used in various fields such as finance, medicine, marketing, among others. They are easy to interpret and explain, and are useful for dealing with problems with many categorical or discrete variables.
- Random Forests:
Random Forest is a machine learning technique based on decision trees. It works by creating multiple decision trees and then combining their predictions to improve the accuracy and stability of the model. Each decision tree is built from a random subset of the training data samples and a random subset of features. This ensures that the trees are different from each other and can capture different patterns in the data.
The final prediction is usually given by the average of the predictions of the individual trees or by the mode of the predictions of the individual trees for classification problems. This typically results in a more robust and accurate model than a single decision tree. Additionally, the random forest technique also allows for feature selection as the individual trees can be used to evaluate the importance of each feature for the final prediction.
- Gradient Boosting:
Gradient Boosting is a machine learning algorithm that is used to increase the accuracy of machine learning models, especially decision tree models. It is based on an iterative process, where each iteration adds an additional model to correct the errors made by previous models.
The algorithm works by creating weak decision tree models and adding them to the final model, where each tree is trained to correct the errors made by previous trees. The algorithm uses the gradient boosting technique, where in each iteration, the current model is adjusted to minimize the loss (error) made by previous models.
The final result is a model composed of many weak decision trees, where each tree is responsible for identifying a subset of the data and improving the accuracy of the final model. Gradient Boosting is widely used in applications such as classification, regression, and anomaly detection due to its ability to handle imbalanced data and categorical features.
