Feature Exploration/Learning

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A feature is an individual measurable property or characteristic of a phenomenon being observed. The concept of a “feature” is related to that of an explanatory variable, which is used in statistical techniques such as linear regression. Feature vectors combine all of the features for a single row into a numerical vector. Part of the art of choosing features is to pick a minimum set of independent variables that explain the problem. If two variables are highly correlated, either they need to be combined into a single feature, or one should be dropped. Sometimes people perform principal component analysis to convert correlated variables into a set of linearly uncorrelated variables. Some of the transformations that people use to construct new features or reduce the dimensionality of feature vectors are simple. For example, subtract Year of Birth from Year of Death and you construct Age at Death, which is a prime independent variable for lifetime and mortality analysis. In other cases, feature construction may not be so obvious. Machine learning algorithms explained | Martin Heller - InfoWorld

Feature Examples

For example, if you were building a machine learning model to predict whether someone would like a particular movie, you might use features like the person's age, gender, and favorite genres of movies. You might also use features about the movie itself, such as the genre, director, and rating. Features are important because they allow machine learning models to learn about the world. By providing models with features, we can teach them to identify patterns and make predictions.

Here is an example of a feature in AI that a 7th grader might understand:

Imagine you are building a machine learning model to predict whether a student will pass or fail a math test. You might use the following features:

  • The student's grades on previous math tests
  • The student's attendance record in math class
  • The student's homework completion rate
  • The student's score on the math portion of the standardized test

Your machine learning model would learn to identify patterns in this data. For example, the model might learn that students who have high grades on previous math tests and good attendance are more likely to pass the test. The model could also learn that students who miss a lot of class or have incomplete homework are more likely to fail the test. Once your machine learning model is trained, you can use it to predict whether a new student is likely to pass or fail the math test. You can do this by providing the model with the student's features, such as their grades on previous math tests and their attendance record. The model will then use this information to make a prediction.

Feature Store

A feature store in AI is a system for managing and serving features to machine learning models. Features are measurable pieces of data that can be used to train and evaluate models. Feature stores provide a central repository for features, making them easier to discover, reuse, and manage. Feature stores are important because they can help to improve the quality, efficiency, and scalability of machine learning development and deployment. For example, feature stores can help to:

  • Reduce the time and effort required to develop and maintain machine learning models
  • Improve the performance and accuracy of machine learning models
  • Make machine learning models more reproducible and scalable
  • Ensure that machine learning models are using consistent and up-to-date data


Offerings:

  • Continual Feature Store: Open source, designed for real-time machine learning
  • Databricks Feature Store: Fully integrated with Databricks
  • FEAST: Open source, cloud-native, scalable and performant
  • FeatureBase: Commercial, offered by Google Cloud, easy to use
  • Feathr: Commercial, offered by AWS, scalable and performant
  • Hopsworks Feature Store: Open source, versatile, offers open APIs
  • Jukebox Feature Store: Commercial, cloud-based, designed for real-time serving
  • Metarank Feature Store: Commercial, cloud-based, designed for machine learning ranking
  • Microsoft Azure Feature Store: Commercial, offered by Microsoft Azure, easy to use
  • Nexus Feature Store: Commercial, cloud-based, designed for large-scale machine learning
  • Salesforce Einstein Feature Store: Commercial, offered by Salesforce, easy to use
  • Vertex AI: Commercial, offered by Google Cloud, part of Vertex AI platform
  • Amazon SageMaker Feature Store: Commercial, offered by AWS, scalable and performant


Use Case: You could store these features in a feature store. This would make it easy to reuse the features for different machine learning models, and it would also make it easier to manage the features over time. For example, if you wanted to add a new feature, such as the student's participation in math class, you could simply add it to the feature store.

Here are some other examples of when you might use a feature store:

  • You are building a machine learning model to predict whether a customer will churn (cancel their subscription). You could use a feature store to store features such as the customer's past purchase history, their engagement with your product, and their support tickets.
  • You are building a machine learning model to recommend products to customers. You could use a feature store to store features such as the customer's past purchase history, their browsing history, and their product ratings.
  • You are building a machine learning model to detect fraud. You could use a feature store to store features such as the customer's transaction history, their device information, and their location.


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Feature Selection

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Recent Advances in Feature Selection: A Data Perspective part 1
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Feature selection is an important step in machine learning model building process. The performance of models depends in the following : Choice of algorithm Feature Selection

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