手法を比較

	二次判別分析 (QDA)	線形判別分析 (LDA)
分野	機械学習	機械学習
系統	Latent structure	Latent structure
提唱年	1939	1936
提唱者	Classical Gaussian discriminant analysis (Fisher / Welch lineage)	Fisher, R. A.
種類	Generative Gaussian classifier	Supervised dimensionality reduction and linear classifier
原典	Hastie, T., Tibshirani, R., & Friedman, J. (2009). The Elements of Statistical Learning (2nd ed.). Springer. ISBN: 978-0-387-84857-0	Fisher, R. A. (1936). The use of multiple measurements in taxonomic problems. Annals of Eugenics, 7(2), 179–188.
別名	QDA, quadratic classifier, kuadratik diskriminant analizi	LDA, Fisher's discriminant analysis, Fisher linear discriminant, normal discriminant analysis
関連	2	4
概要	Quadratic discriminant analysis is a generative classifier that models each class with its own multivariate Gaussian distribution, allowing each class a separate covariance matrix. Unlike linear discriminant analysis, which assumes a shared covariance and yields linear boundaries, QDA's per-class covariances produce curved (quadratic) decision boundaries, letting it capture differences in the spread and orientation of the classes.	Linear Discriminant Analysis is a supervised method for dimensionality reduction and classification, introduced by Ronald A. Fisher in 1936, that finds linear combinations of features which maximally separate predefined classes while preserving as much class-discriminatory information as possible. It simultaneously serves as a feature-projection technique and a probabilistic classifier, making it one of the foundational methods in pattern recognition and statistical learning.