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Weka (software)
Weka (software)
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Weka
DeveloperUniversity of Waikato
Stable release
3.8.6 (stable) / January 28, 2022; 4 years ago (2022-01-28)
Preview release
3.9.6 / January 28, 2022; 4 years ago (2022-01-28)
Written inJava
Operating systemWindows, macOS, Linux
PlatformIA-32, x86-64, ARM_architecture; Java SE
TypeMachine learning
LicenseGNU General Public License
Websiteml.cms.waikato.ac.nz/weka
Repository

Waikato Environment for Knowledge Analysis (Weka) is a collection of machine learning and data analysis free software licensed under the GNU General Public License. It was developed at the University of Waikato, New Zealand and is the companion software to the book "Data Mining: Practical Machine Learning Tools and Techniques".[1]

Description

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Weka contains a collection of visualization tools and algorithms for data analysis and predictive modeling, together with graphical user interfaces for easy access to these functions.[1] The original non-Java version of Weka was a Tcl/Tk front-end to (mostly third-party) modeling algorithms implemented in other programming languages, plus data preprocessing utilities in C, and a makefile-based system for running machine learning experiments. This original version was primarily designed as a tool for analyzing data from agricultural domains,[2][3] but the more recent fully Java-based version (Weka 3), for which development started in 1997, is now used in many different application areas, in particular for educational purposes and research. Advantages of Weka include:

  • Free availability under the GNU General Public License.
  • Portability, since it is fully implemented in the Java programming language and thus runs on almost any modern computing platform.
  • A comprehensive collection of data preprocessing and modeling techniques.
  • Ease of use due to its graphical user interfaces.

Weka supports several standard data mining tasks, more specifically, data preprocessing, clustering, classification, regression, visualization, and feature selection. Input to Weka is expected to be formatted according the Attribute-Relational File Format and with the filename bearing the .arff extension. All of Weka's techniques are predicated on the assumption that the data is available as one flat file or relation, where each data point is described by a fixed number of attributes (normally, numeric or nominal attributes, but some other attribute types are also supported). Weka provides access to SQL databases using Java Database Connectivity and can process the result returned by a database query. Weka provides access to deep learning with Deeplearning4j.[4] It is not capable of multi-relational data mining, but there is separate software for converting a collection of linked database tables into a single table that is suitable for processing using Weka.[5] Another important area that is currently not covered by the algorithms included in the Weka distribution is sequence modeling.

Extension packages

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In version 3.7.2, a package manager was added to allow the easier installation of extension packages.[6] Some functionality that used to be included with Weka prior to this version has since been moved into such extension packages, but this change also makes it easier for others to contribute extensions to Weka and to maintain the software, as this modular architecture allows independent updates of the Weka core and individual extensions.

History

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  • In 1993, the University of Waikato in New Zealand began development of the original version of Weka, which became a mix of Tcl/Tk, C, and makefiles.
  • In 1997, the decision was made to redevelop Weka from scratch in Java, including implementations of modeling algorithms.[7]
  • In 2005, Weka received the SIGKDD Data Mining and Knowledge Discovery Service Award.[8][9]
  • In 2006, Pentaho Corporation acquired an exclusive licence to use Weka for business intelligence.[10] It forms the data mining and predictive analytics component of the Pentaho business intelligence suite. Pentaho has since been acquired by Hitachi Vantara, and Weka now underpins the PMI (Plugin for Machine Intelligence) open source component.[11]
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See also

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References

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Revisions and contributorsEdit on WikipediaRead on Wikipedia
from Grokipedia
Weka is an open-source collection of algorithms and tools designed for solving real-world problems, developed by the in . Written primarily in , it runs on virtually any platform and is licensed under the version 3.0, enabling free use, modification, and distribution for research, education, and practical applications. The software, whose name stands for Waikato Environment for Knowledge Analysis and is pronounced like the native , provides a user-friendly graphical interface alongside programmatic access via Java APIs. Initiated in 1992 by a team at the including key contributors such as Ian H. Witten and Eibe Frank, Weka's development began as a mix of Tcl/Tk, C, and makefiles before transitioning to a fully Java-based implementation with version 3.0 in 1999. The first public release, version 2.1, occurred in October 1996, followed by stable updates like version 3.4 in 2003 and version 3.6 in 2008; the latest stable release is version 3.8.6 (January 2022), with ongoing enhancements through a package management system for extensions. In 2006, Weka was adopted by Corporation for integration into their tools, broadening its application in enterprise environments. Its enduring popularity stems from a development history spanning over three decades, supported by an active open-source community of developers including Remco R. Bouckaert, Mark A. Hall, Geoffrey Holmes, Bernhard Pfahringer, Peter Reutemann, and others. At its core, offers a workbench with components like the Explorer for interactive , the Experimenter for comparative evaluations of algorithms, and the Knowledge Flow for visual workflow construction, facilitating tasks from data preprocessing to model deployment. Key features include support for formats such as ARFF (Attribute-Relation File Format), CSV, and database connections; a wide array of algorithms for classification (e.g., decision trees, naive Bayes, support vector machines via LibSVM), regression, clustering (e.g., k-means), association rule mining (e.g., Apriori), and attribute selection; as well as preprocessing filters, visualization tools, and export options like PMML for model sharing. These capabilities make it particularly suitable for educational purposes and exploratory analysis, though it is less optimized for massive-scale production compared to specialized libraries. Weka's significance in the machine learning community is underscored by its receipt of the 2005 ACM SIGKDD Service Award for advancing practices through accessible tools and techniques. It has been downloaded millions of times since its inception, influencing textbooks like Data Mining: Practical Tools and Techniques by its primary developers, and serving as a benchmark for and in academia and industry. The project's extensibility via user-contributed packages—managed through an integrated tool—allows seamless incorporation of new s, such as those for multi-instance learning and Bayesian methods, ensuring its in evolving fields like predictive modeling and pattern discovery.

Overview

Description

Weka is a free, open-source collection of algorithms designed for and analysis tasks, developed at the in . The software's name stands for Waikato Environment for Knowledge Analysis, and it draws inspiration from the , a native to known for its inquisitive nature. Its core purpose is to facilitate data preprocessing, , regression, clustering, association rule mining, and visualization, making it particularly suitable for educational and research applications in . Weka primarily utilizes the Attribute-Relation File Format (ARFF), an ASCII text-based format that describes datasets with attributes and instances, enabling straightforward data handling and integration. Among its general advantages are a user-friendly graphical interface that lowers the entry barrier for beginners and a comprehensive suite of tools that support practical workflows in academic and exploratory settings.

Licensing and Platform Support

Weka is distributed under the GNU General Public License version 3 (GPLv3), an that allows users to freely use, study, modify, and distribute the software, including for commercial purposes, as long as any modifications are released under the same license terms. This licensing model fosters widespread adoption in academic and research settings while ensuring the software remains freely accessible. Developed entirely in , Weka exhibits strong cross-platform compatibility, running on any operating system supported by the (JVM), such as Windows, macOS, and various distributions, without requiring platform-specific recompilation. This portability enables seamless deployment across diverse hardware architectures and environments. Installation of Weka necessitates a Java Runtime Environment (JRE) version 8 or later, with higher versions recommended for optimal performance and compatibility with graphical user interfaces, particularly on high-resolution displays. Official distributions, including installers and source code, are hosted on , providing straightforward access for users worldwide. The project is primarily maintained by the Group at the in , supplemented by contributions from an international developer community through its open-source repositories.

History

Development Origins

Weka originated in 1993 at the in , where it was initiated as a practical workbench to support teaching and research in . The project received funding from the starting that year, with development of the initial interface and algorithms commencing shortly after Ian Witten applied for support in late 1992. The name WEKA stands for Waikato Environment for Knowledge Analysis, reflecting its roots in the local academic environment. The software's early implementation focused on rapid prototyping of techniques, utilizing Tcl/Tk for the to enable quick development and user interaction, while core learning algorithms were primarily written in C, with additional components in C++ and . This modular design allowed for an integrated environment where users could experiment with various schemes on real-world datasets, including the newly introduced Attribute-Relation File Format (ARFF) developed by Andrew Donkin in 1993. The first internal release occurred in 1994, marking the transition from concept to functional tool. The primary motivations behind Weka's creation were to apply to practical problems, particularly in and , while shifting focus from supporting machine learning researchers to empowering end users and domain specialists who lacked deep expertise in the field. By providing an accessible collection of state-of-the-art algorithms and preprocessing tools under a unified interface, the project aimed to democratize machine learning for non-experts in academia, facilitating exploration of fielded applications and the discovery of new methods without the barriers of complex programming. This emphasized and interpretability to bridge the gap between theoretical techniques and real-world . Weka was conceived as companion software to the textbook Data Mining: Practical Machine Learning Tools and Techniques by Ian H. Witten, Eibe Frank, and colleagues, incorporating virtually all the algorithms and data preprocessing methods detailed in the book to serve as a hands-on resource for its concepts. This integration supported the book's emphasis on practical , allowing readers to directly implement and test techniques described in its chapters.

Major Releases and Milestones

The first public release, version 2.1, occurred in October 1996. In 1997, the development team at the decided to redevelop the software from scratch in to enhance portability across platforms via the and to simplify maintenance and integration with external libraries, replacing the previous unwieldy C-based implementation that relied on Tcl/Tk for its graphical interface. Version 3.0, released in mid-1999, marked a significant as the first fully Java-based version, introducing a (GUI) and expanding support for a broader range of algorithms, which accompanied the first edition of the foundational textbook by the team. A key advancement came with version 3.7.2 in July 2010, which introduced the package management system, allowing users to easily install and manage extensions for additional functionality without modifying the core software. In 2016, integration of capabilities via the WekaDeeplearning4j package enabled support for neural networks, including convolutional architectures, leveraging the library to bring modern techniques into the Weka ecosystem. In 2005, the team received the ACM SIGKDD Data Mining and Knowledge Discovery Service Award, recognizing its substantial educational impact and widespread adoption in teaching and research. The following year, in 2006, (now part of Vantara) acquired an exclusive license to incorporate into its suite, facilitating commercial integrations and broader enterprise use while the open-source project continued independently. As of January 2022, the stable release was version 3.8.6, with developer preview 3.9.6 released concurrently, focusing on refinements and bug fixes rather than major new features. By November 2025, no major public updates had been issued beyond these versions, though ongoing maintenance and minor enhancements continue through the project's official repository hosted by the .

Core Features

Algorithms and Tasks

Weka provides a comprehensive suite of machine learning algorithms categorized primarily into supervised and unsupervised learning, with support for semi-supervised approaches through certain meta-learners and filters. Supervised learning encompasses tasks like classification and regression, where models are trained on labeled data to predict outcomes, while unsupervised learning focuses on clustering and association rule discovery to uncover patterns in unlabeled data. Ensemble methods, such as bagging and boosting, are integrated to enhance model performance by combining multiple base learners, exemplified by the RandomForest algorithm which builds an ensemble of decision trees to reduce overfitting and improve generalization. Data preprocessing is a foundational task in Weka, enabling data cleaning, transformation, and normalization to prepare datasets for . Core filters include attribute filters like Normalize for scaling numeric attributes to a standard range and NominalToBinary for converting categorical variables into binary representations, as well as supervised filters such as Discretize which bins numeric attributes based on class information. These preprocessing tools handle common issues like missing values via ReplaceMissingValues and detection through InterquartileRange, ensuring without requiring external scripting. For , Weka implements methods like information gain, which ranks attributes by their ability to reduce in , and chi-squared testing to evaluate attribute-class , allowing users to identify the most predictive features and mitigate dimensionality. In , Weka supports a range of algorithms for predicting categorical outcomes, including the J48 decision tree, an optimized implementation of the that uses information gain for splitting and post-pruning to simplify trees, and the , which applies under the assumption of attribute independence for probabilistic predictions. Regression tasks address numeric prediction, with built-in support for , which fits a minimizing squared errors, and for binary (and multinomial) outcomes using classifiers like SimpleLogistic. These algorithms are applicable to diverse domains, such as for or stock price forecasting for regression. Unsupervised learning in Weka includes clustering algorithms like k-means, which partitions data into k groups by minimizing intra-cluster variance through iterative centroid updates, and , which builds a of clusters using linkage criteria such as single or complete linkage. Association rule mining is facilitated by the , which identifies frequent itemsets and generates rules meeting minimum support and confidence thresholds, commonly used for analysis. Semi-supervised capabilities are available through certain meta-learners and wrappers, with extensive options in packages that leverage limited to guide unsupervised processes. Weka handles input primarily through the Attribute-Relation File Format (ARFF), an ASCII-based structure that supports nominal (categorical), numeric (continuous or integer), string (textual), and date attributes, allowing flexible representation of heterogeneous datasets. It also integrates with CSV files for simple tabular imports and SQL databases via JDBC loaders, enabling direct querying and loading of relational without manual conversion. This multi-format support facilitates seamless workflow from data ingestion to modeling. Model evaluation in Weka employs metrics and techniques to assess performance rigorously, including k-fold cross-validation, which partitions data into k subsets for training and testing to estimate unbiased accuracy by averaging results across folds. For , accuracy measures overall correctness, while precision-recall curves evaluate performance on imbalanced datasets by plotting precision (true positives over predicted positives) against (true positives over actual positives). (ROC) curves visualize the trade-off between true positive rate and false positive rate across thresholds, aiding in threshold selection for probabilistic classifiers like Naive Bayes. These methods provide a balanced view of model reliability without assuming equal class distributions.

User Interfaces and Tools

Weka provides multiple user interfaces to facilitate interaction with its capabilities, catering to both novice users through graphical tools and advanced users via programmatic access. These interfaces enable data exploration, , , and visualization without requiring deep programming knowledge in many cases, while also supporting scripting and integration into larger applications. The primary graphical user interface, known as the Explorer, offers an interactive environment for tasks. Users can load datasets in ARFF format, preprocess data using filters for tasks like normalization or attribute selection, and apply classifiers, clusterers, or association rule learners through menu selections and form-based inputs. It supports simple workflows by allowing step-by-step model training, testing via cross-validation or hold-out methods, and immediate result inspection, making it suitable for exploratory analysis. Complementing the Explorer, the Experimenter interface is designed for batch evaluations and comparative studies. It enables users to configure experiments across multiple datasets and algorithms, specifying parameters such as evaluation metrics (e.g., accuracy, precision) and repetition schemes like 10-fold cross-validation. Results are compiled into tables for statistical , including t-tests for significance, and can be exported for further processing, facilitating systematic performance comparisons. For more complex workflows, the Knowledge Flow serves as a visual . Users drag and drop components—such as data sources, filters, learners, and evaluators—onto a and connect them via directed links to form processing pipelines. This supports incremental and streamed , allowing real-time execution and monitoring of data flows, which is particularly useful for building reusable pipelines. Weka also includes a for scripting and automation. Accessed via commands, it allows direct invocation of algorithms, such as running a classifier on a with options for output formatting (e.g., java weka.classifiers.trees.J48 -t data.arff -x 10), enabling in non-interactive environments like servers or scripts. Integrated visualization tools enhance model interpretation across these interfaces. The Explorer and Knowledge Flow provide matrices for attribute relationships, Jittered plots for nominal data, histograms for distributions, and visualizers for displaying structures with node statistics. Boundary plot visualizers generate contour plots to illustrate classifier decision boundaries in two-dimensional feature spaces, aiding in understanding model behavior. For programmatic use, exposes a comprehensive , allowing embedding in custom applications. Core classes like Instances represent datasets, enabling loading and manipulation, while Classifier and Filter interfaces support training models and applying transformations. A basic example involves creating an Instances object from a file, building a classifier (e.g., via classifier.buildClassifier(instances)), and making predictions on test data. This facilitates integration into or research prototypes.

Extensions and Packages

Package Management System

The package management system in Weka was introduced in version 3.7.2, released in 2010, to facilitate the modular extension of the core software by allowing users to browse, install, and update additional functionality through a built-in (GUI) accessible via the Tools menu in the GUIChooser. This system separates extensions from the main weka.jar file, enabling a lighter core distribution while supporting of new algorithms, tools, and resources at runtime without requiring recompilation or modifications. A is also provided through the java weka.core.WekaPackageManager class, supporting operations such as listing packages (-list-packages), installing by name or URL (-install-package), and refreshing the local cache (-refresh-cache). The central repository for official packages is hosted on , with metadata cached locally for efficient access, and many packages also maintain development repositories on . As of the latest updates, this repository contains over 200 official packages, categorized by function such as , clustering, regression, visualization, and attribute selection, allowing users to extend Weka's capabilities in targeted areas like advanced techniques or data preprocessing tools. Installation occurs seamlessly via the GUI or CLI, where users can specify a package name, local ZIP file, or remote ; the automatically resolves and installs dependencies, though this can be optionally disabled in the GUI for custom setups. Packages are distributed as self-contained archives including files, , and metadata files (e.g., PackageDescription.props), which are loaded dynamically at runtime to integrate with Weka's . Offline mode has been supported since version 3.7.8, enabled via the -offline CLI or the weka.packageManager.offline=true , allowing installations from pre-downloaded files without . Maintenance of the system emphasizes stability and community involvement, with unofficial packages installable through the GUI's "File/url" option—bypassing dependency checks for flexibility—often contributed by third-party developers and integrated via the official repository after review. Updates to packages are versioned and tied to compatible releases, ensuring with the core without disrupting existing installations; users are notified of available updates starting from version 3.7.3, and a restart of may be required post-upgrade to fully load changes.

Notable Extensions

Weka's ecosystem has been significantly expanded through its package management system, enabling the development and distribution of specialized extensions that address limitations in the core software, such as handling , advanced neural networks, and domain-specific tasks. One of the most prominent extensions is Auto-WEKA, which automates the combined algorithm selection and (CASH) problem using to identify optimal models for , regression, and attribute selection without requiring expert intervention. This package has democratized access to high-performance pipelines, particularly for non-experts, by searching through Weka's algorithm space and tuning parameters efficiently. Another key extension is the integration with Massive Online Analysis (MOA), which brings support for streaming data mining and online learning directly into Weka's interfaces, allowing users to apply incremental classifiers to evolving data streams that exceed memory limits. MOA enables real-time processing of massive datasets, filling a critical gap in Weka's batch-oriented core by incorporating algorithms for concept drift detection and adaptive learning. Within this integration, MOA Text provides specialized tools for text classification in streaming contexts, such as bag-of-words representations and incremental naive Bayes variants tailored for high-velocity textual data. For deep learning capabilities, the WekaDeeplearning4j package leverages the Deeplearning4j backend to incorporate neural networks, including convolutional and recurrent architectures, with GPU acceleration and a for training and evaluation. This extension bridges Weka's traditional focus on classical with modern techniques, supporting tasks like image and sequence classification while maintaining compatibility with Weka's workflow. Other notable packages include Meka, which extends to multi-label and multi-target classification by providing a suite of algorithms, evaluation metrics, and transformation methods for scenarios where instances associate with multiple labels simultaneously. Similarly, the Machine Learning (TSML) tools, including the timeseriesForecasting package, offer wrappers for regression schemes that automate lag variable creation and forecasting, enabling effective analysis of temporal data patterns. By 2025, the Weka community has contributed over 214 packages, collectively enhancing the platform's versatility for big data handling, distributed computing interfaces, and domain-specific applications like bioinformatics, thereby sustaining its relevance in diverse research and practical settings.

Integrations with Other Software

Weka supports direct integration with relational databases through its JDBC (Java Database Connectivity) interface, enabling users to load data via SQL queries from compatible sources such as MySQL and PostgreSQL. To establish a connection, users must include the appropriate JDBC driver in the classpath and configure a customized DatabaseUtils.props file, which includes predefined settings for databases like MySQL (Weka version 3.4.9 or later) and PostgreSQL (Weka version 3.4.9 or later). This allows seamless importation of data into Weka's ARFF format for analysis without manual file exports. In commercial business intelligence environments, Weka is embedded within Pentaho Data Integration (PDI), now part of Hitachi Vantara's suite, to operationalize machine learning models alongside data orchestration tasks. PDI incorporates Weka's algorithms directly through its plugin framework, supporting the execution of classification, regression, and clustering workflows within ETL (Extract, Transform, Load) pipelines, with performance optimizations for large datasets to avoid memory issues. Additionally, Hitachi Vantara's Pentaho Machine Intelligence (PMI) leverages Weka for blending structured and unstructured data sources in predictive analytics, enabling early detection applications in industries like equipment maintenance. Weka's core Java implementation provides a comprehensive API for embedding its functionality into custom applications, allowing developers to invoke classifiers, filters, and evaluation tools programmatically. For R users, the RWeka package serves as an interface, providing access to Weka's algorithms (version 3.9.3) for tasks like and clustering directly from scripts, requiring the RWekajars package for the underlying components. In Python ecosystems, the python-weka-wrapper3 library enables integration by wrapping Weka's non-GUI features via the JPype bridge to the , supporting 11 or later and Weka 3.9.6, while the sklearn-weka-plugin extends this compatibility to pipelines for hybrid workflows. The Weka Data Mining Integration extension, which incorporated Weka's framework (version 3.7) as nodes for analytical pipelines, has been deprecated and is no longer recommended for use. Model compatibility with other frameworks like is facilitated via (Predictive Model Markup Language) support, allowing export of Weka models (such as regression and neural networks) for import into or vice versa, ensuring interoperability in multi-tool environments.

Comparisons with Alternatives

Weka distinguishes itself from , a prominent Python-based , primarily through its user-friendly (GUI), which enables non-programmers to explore algorithms interactively without coding. , in contrast, excels in programmatic flexibility, leveraging Python's ecosystem for efficient scripting, model deployment, and scalability on large datasets via optimized numerical libraries like . Academic evaluations show comparable predictive performance across algorithms in both tools, but often outperforms in handling high-dimensional data due to its integration with frameworks. Compared to , an open-source data science platform with commercial extensions, Weka remains fully free and lightweight, ideal for resource-constrained environments and quick prototyping. provides superior visual workflow design and extensive preprocessing operators, including advanced and process automation, making it suitable for enterprise-level analytics, though its full capabilities often require paid licenses. Studies on tasks indicate Weka achieves similar accuracy to on standard datasets but with simpler setup, while handles complex pipelines more intuitively for interdisciplinary teams. Both and Orange emphasize intuitive GUIs for , targeting users who prefer visual exploration over command-line interfaces. 's Java-centric architecture facilitates seamless integration with applications and enterprise systems, supporting formats like ARFF for structured data representation. Orange, built on Python and Qt, prioritizes widget-based visual scripting for customizable data flows, offering stronger support for interactive visualizations and add-ons in statistical analysis. Comparative analyses highlight 's edge in algorithmic breadth for educational and settings, while Orange simplifies pipeline construction for exploratory . Weka's unique strengths include its educational orientation, often bundled with textbooks like "Data Mining: Practical Machine Learning Tools and Techniques" for teaching core concepts in , clustering, and association rules, and the ARFF format, which standardizes attribute-relation data in a human-readable text for easy preprocessing and sharing. However, Weka faces limitations in native processing due to its single-machine design, struggling with datasets beyond gigabyte scales without memory issues; these are partially mitigated by community extensions like distributed wrappers for , enabling scalable execution on clusters. In terms of adoption, enjoys broad use in academia, with millions of downloads since 2000 and integration into university curricula for hands-on experiments, fostering its role in . Industry adoption is more niche, favoring for prototyping in environments, but deep learning-dominant tools like prevail for production-scale applications requiring GPU acceleration and massive datasets.

References

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