Types of Machine Learning

Machine learning algorithms can be trained in a variety of ways, each with advantages and disadvantages. Machine learning is broadly classified into four groups based on these methodologies and modes of learning:

1. Supervised Learning

This type of ML is supervised, in which machines are taught on labelled datasets and then allowed to predict outputs based on the training. Certain input and output parameters are already mapped, according to the labelled dataset. As a result, the machine is taught using the input and output. In later rounds, a device is created to predict the outcome using the test dataset.

Consider the following input dataset: parrot and crow photos. Initially, the system is trained to recognize the images, which include the color, eyes, shape, and size of the parrot and crow. Following training, an image of a parrot is presented as input, and the machine is expected to identify the object and forecast the output. To create a final prediction, the trained computer examines the input image for numerous aspects of the object, such as colour, eyes, shape, and so on. In supervised machine learning, this is the process of identifying objects.

The supervised learning technique’s primary goal is to translate the input variable (a) to the output variable (b). There are two broad categories of supervised machine learning:

• Classification algorithms are those that address classification issues with categorical output variables, such as yes or no, true or false, male or female, and so on. This category’s real-world applications include spam detection and email filtering.
  The Random Forest Algorithm, Decision Tree Algorithm, Logistic Regression Algorithm, and Support Vector Machine Algorithm are some well-known classification algorithms.
• Regression algorithms deal with regression situations in which the input and output variables have a linear relationship. These are well-known predictors of continuous output variables. Weather forecasting, market trend research, and other applications are examples.
  The Simple Linear Regression Algorithm, Multivariate Regression Algorithm, Decision Tree Algorithm, and Lasso Regression are all popular regression techniques.

2. Unsupervised Learning

Unsupervised learning is a learning strategy that does not require supervision. In this case, the machine is trained on an unlabeled dataset and is able to predict the output without human intervention. An unsupervised learning algorithm attempts to group the unsorted dataset based on similarities, differences, and patterns in the input.

Consider the following input dataset: photos of a fruit-filled container. The photos in this case are unknown to the machine learning model. When we feed the dataset into the ML model, the model’s objective is to recognise and categorise the patterns of objects seen in the input photographs, such as colour, form, or differences. Following categorization, the machine predicts the output while being tested with a test dataset.

Unsupervised machine learning is further classified into two types:

• Clustering:  Clustering refers to the process of arranging things into clusters based on characteristics such as similarities or contrasts between objects. For example, grouping clients based on the products they buy.
  The K-Means Clustering Algorithm, Mean-Shift Algorithm, DBSCAN Algorithm, Principal Component Analysis, and Independent Component Analysis are some well-known clustering techniques.
• Association:  Association learning is the process of detecting typical relationships between variables in a big dataset. It determines the interdependence of several data items and maps the variables connected with them. Web usage mining and market data analysis are two examples of typical applications.
  The Apriori Algorithm, Eclat Algorithm, and FP-Growth Algorithm are examples of popular algorithms that follow association principles.

3. Semi-supervised Learning

Semi-supervised machine learning combines aspects of both supervised and unsupervised machine learning. It trains its algorithms using a combination of labelled and unlabeled datasets. Semi-supervised learning solves the disadvantages of the preceding solutions by using both types of datasets.

Consider the following example of a college student. In college, supervised learning refers to a student learning an idea under the observation of an instructor. Unsupervised learning occurs when a student learns the same idea at home without the assistance of an instructor. Meanwhile, at college, a student reviewing the concept after learning under the supervision of an instructor is a semi-supervised form of learning.

4. Reinforcement Learning

Reinforcement learning is a process that is based on feedback. Here, the AI component uses the hit-and-trial method to automatically assess its surroundings, take action, learn from experiences, and improve performance. The component is awarded for each correct action and penalised for each incorrect move. As a result, the reinforcement learning component seeks to maximise rewards by completing positive activities.

Unlike supervised learning, reinforcement learning does not use labelled data, and agents learn only via their experiences. Take, for example, video games. The game defines the environment in this case, and each move of the reinforcement agent defines its state. The agent is entitled to input in the form of punishment and rewards, which affects the total game score. The agent’s ultimate goal is to get a high score.

Reinforcement learning is used in a variety of domains, including game theory, information theory, and multi-agent systems. Reinforcement learning methods or algorithms are further classified as follows:

• Positive reinforcement learning:  Adding a reinforcing stimulus after a certain behavior of the agent increases the likelihood that the behavior will occur again in the future, for example, adding a reward after a behavior.
• Negative reinforcement learning:  Negative reinforcement learning is the practise of improving a specific habit in order to prevent a negative outcome.