Active Learning – Short Explanation

Active Learning is a machine learning (ML) technique where the algorithm can select data it wants to learn from. In active learning, the algorithm chooses which subset of examples to label next from the pool of previously unclassified data. Passive learning is different in that a user gives all known parameters as training labels without considering how useful this will be for future prediction.

The idea behind active learning

The basic idea behind the active learner algorithm is that an ML algorithm may achieve a higher level of accuracy while working with a smaller number of training labels if given free rein to select the data it wishes to learn. The program may use this approach to query an authoritative source, such as a labelled dataset, in order to obtain the correct prediction for a certain problem.

The aim of this iterative learning technique is to speed up learning by minimizing the amount of time spent on data preparation and algorithm tuning. The trade-off is that an active learner algorithm typically takes more time to find the best training labels.

Active learning requirements

One of the most important considerations when using active learning is the quality of the data. To be effective, the data must be well-distributed across different classes so that the algorithm can identify relevant examples easily. If the data isn’t well-distributed, then it may be difficult for the algorithm to find good examples of each class, which could lead to poorer performance on later predictions.


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How active learning works

Active learning works by giving the algorithm a starting point of labeled data. This forced choice is called an active instance, and the goal of the learner is to select as few as possible. The more it chooses, the higher its risk of mislabeling examples and deteriorating its performance on future predictions.

Active learning algorithms are better at learning from data sets with a lot of uncertainty. This is because they focus on instances that are most likely to lead to improved predictions. The four most common types of active learning algorithms are selective sampling, iterative refinement, uncertainty sampling, and query by committee. Each type has its own strengths and weaknesses:

  • Selective Sampling – The algorithm randomly selects a small number of instances from the data set and labels them. It then uses those instances to train the model.
  • Iterative-Refinement – The algorithm starts by selecting a random instance as the active instance. It then compares the prediction error on that instance to the prediction error on all of the other instances in the data set. If it finds a more accurate prediction on another instance, it reclassifies that instance as active and repeats the process.
  • Uncertainty Sampling – The algorithm randomly selects a small number of instances from the data set and labels them. It then uses those instances to train the model.
  • Query by Committee – The algorithm starts by selecting a random instance as the active instance. It then splits the data set into clusters, where each cluster contains similar instances. It then selects one active instance from each cluster.

The active learning loop

The active learning loop consists of acquiring some labeled data and using that to train a model. The model is interrogated for insights about what new examples would be useful, which is then sent over to a human to label.

The active learning loop can be used in a variety of machine learning applications such as classification, regression, clustering, anomaly detection, data cleaning, auto-mapping etc.

Active Learning Loop

Which method is best?

There’s no one-size-fits-all answer to this question. Different methods will work better for different models, and each method has its pros and cons. For example, uncertainty sampling works best when there are many examples that are all very similar to the instance you’re trying to classify. It doesn’t perform as well for models where some training instances contain more information than others (e.g., neural networks).

The good and bad of active learning

Active Learning performs best when it’s possible to find a good representative of the data set (i.e., one with a high margin or low complexity). It also scales well to large numbers of labelled instances while preserving computational resources by focusing on the most informative examples first. However, it requires some subject-matter knowledge about the task at hand in order to make an informed choice about which instance is best for labeling.

The idea behind Active Learning is to have the user chooses which instance to annotate, hence choosing the most informative.

First, let’s define what an active learner is – in the context of machine learning; it refers to a model that helps label AI training data by querying its owner. For example, if you are trying to build a spam detector, one approach would be to ask human users whether email messages are spam or not. If, however, you could ask only a subset of the users, this would be an active learning technique called “selective sampling”, since it selects instances based on their predicted usefulness for labeling.

One advantage of selective sampling over full coverage is that it can save time and cost while achieving the same or better accuracy. The main disadvantages are that it requires an oracle to tell the difference between important data and redundant data and that it is only applicable when there are enough labels to be had elsewhere.

What are some common active learning algorithms?

Decision Trees

Decision trees are a type of supervised learning algorithm that can be used for both classification and regression tasks. The aim is to create a model that predicts the value of a target variable based on several input variables.

Decision trees are built using a recursive partitioning method. The algorithm starts at the root node and splits the data into two or more subsets. The splits are based on the values of the input variables. The process is then repeated for each subset until the leaves are reached. The leaves represent the decisions or predictions that are made.

Decision trees are a popular choice for machine learning tasks as they are easy to interpret and can be used to make decisions even if the underlying data is complex.

Naive Bayes

Naive Bayes is a classification algorithm that is used to predict the probability of a data point belonging to a particular class. It is a supervised learning algorithm that is trained on a dataset and then used to predict the class of new data points.

Naive Bayes is a simple and effective algorithm that can be used for a variety of tasks such as spam detection, text classification, and sentiment analysis.

Logistic Regression

Logistic regression is a classification algorithm used to assign labels to data points. The algorithm outputs a probability that a data point belongs to a particular class. Logistic regression is a linear algorithm, which means that it makes predictions based on a linear combination of the input features.

Logistic regression is a powerful algorithm that can be used for both binary classification (two classes) and multi-class classification (more than two classes). The algorithm is also robust to outliers, meaning that it can still make accurate predictions even if there are outliers in the data.

Support Vector Machines

Support Vector Machines (SVMs) are a type of supervised machine learning algorithm that can be used for both classification and regression tasks. The algorithm is based on finding a hyperplane that best separates the data into classes.
SVMs are more effective in high dimensional spaces and can be used with non-linear data. They are also relatively robust to over-fitting.

K-Nearest Neighbors

K-Nearest Neighbors is a supervised learning algorithm used for both classification and regression. The algorithm is trained on a data set and then makes predictions based on the similarity of new data points to the points in the training set.

K-Nearest Neighbors is a non-parametric algorithm, which means that it makes no assumptions about the underlying data. This makes it a good choice for data that is not linearly separable. The algorithm is also relatively simple to implement and can be used with a small amount of data.

Neural Networks

Some common active learning algorithms used in neural networks are the delta rule, the perceptron, and the backpropagation algorithm. The delta rule is used to update the weights of the neurons in the network. The perceptron is used to classify the data. The backpropagation algorithm is used to find the error in the network.

Active learning use cases

Active learning has found a number of applications in areas such as text categorization, document classification, and image recognition. It has also been used for cancer detection and drug discovery.

Text Categorization

One of the most common applications of active learning is text categorization, which is the task of assigning a category to a piece of text. In this application, the categories are usually a set of predefined labels such as “news”, “sports”, “entertainment”, and “opinion”. The goal is to automatically assign each piece of text to one of these categories.

Document Classification

Active learning can also be used for document classification, which is the task of automatically assigning a class to a document. In this application, the classes are usually a set of predefined labels such as “technical document”, “marketing document”, and “legal document”.

Image Recognition

Image recognition is another area where active learning can be used. In this example, we have an image and we’d like our annotators to label only relevant regions in the image. In other words, we need to make sure that each labeled region contributes maximum information for classifying the image. To achieve this objective, active learning will pick up the most interesting regions from unlabelled data and let them be processed by annotators.

This way, annotators don’t waste any time on labeling redundant parts of an image that would have remained untagged if they were just blindly assigning labels to all regions in an image.


Active Learning is a technique where the machine itself decides which are the most important data points to be labelled by a human. This has multiple benefits over traditional methods of Machine Learning. However, there’s still much research to be done in this area in order to determine which tasks and datasets are best suited for active learning approaches.

One question that remains unanswered is whether or not Active Learning always outperforms traditional methods – this is still an open question that requires further study. Additionally, it’s also not clear how well Active Learning scales with increasing data sizes. More work is needed in order to better understand the benefits and limitations of Active Learning approaches. Despite these uncertainties, Active Learning is a promising field that has already shown great potential for improving the accuracy of Machine Learning models.

Summary – Active Learning: Deep Learning is a type of Machine Learning that allows computers to learn on their own. Deep learning methods like Active Learning are typically used to solve very complicated problems with numerous variables. With active learning, the machine itself can determine which data points should be labelled, helping save time and effort.


How does active learning compare to weak supervision?

Weak supervision is when you start with unlabeled data and then add in sources of weak supervision to improve the accuracy of the model.
The trade-off is that the models trained with weak supervision are less accurate than those trained with traditional methods.

What are active learning algorithms?

Active learning algorithms are machine learning algorithms that actively learn from feedback. They use a model to predict how people will behave, and they update their predictions based on what they observe. Common active learning algorithms include active-learning algorithms, reinforcement learning, and Bayesian networks. What are some challenges associated with using active learning?
To adapt your model for active learning, you would need a communication channel between annotators and your model so that they can teach each other what changes have been made on their respective side of the equation.

Why to use active learning?

Active learning is a neural network pattern recognition technique as well as a machine-learning methodology employed to make the most effective use of the data and eliminate bias. It is a data-driven approach that is initiated by the user who can be more selective in the use of data, which is “the act of selecting which are to be used to solve a task.” The advantage to using a technique like active learning “is that many problems, like recognizing objects in pictures or facial recognition, are easier the more data is used. With enough data, all the variants of a desired pattern will be found by a machine-learning algorithm. So, “passive” neural networks that only use a dataset as it is provided will usually find only 70% or so of all the desired patterns. “Active” neural networks that select relevant data will often find almost all desired patterns. The trade-off is that active learning takes more time to find the desired patterns.

Excursion: Active learning in the classroom

Active learning in the classroom is a type of learning that involves the learner being actively engaged in the learning process, as opposed to being a passive recipient of information.
Active learning can take many different forms, but some common examples include things like discussions, role-playing, and simulations.

Active learning has been shown to be more effective than traditional, passive methods of learning, such as lectures. This is because it allows learners to be more engaged with the material, and it also allows them to better retain the information.
Active learning is especially important in the classroom, as it can help to keep students engaged and motivated. It can also help to promote higher-level thinking, such as analysis and synthesis.