symmetric matrix concept
| Definition | A square matrix equal to its own transpose. Its eigenvalues are real, its eigenvectors can be chosen orthonormal, and it is the sum of its eigenvalues times the outer products of its eigenvectors. Almost every matrix in the book is one. Primer L, equation L.14. Also symmetric. |
|---|---|
| Example | The matrix with rows (2, 1) and (1, 2) is symmetric, and the one with rows (2, 1) and (0, 2) is not. |
| Book | Data Mining as Observation, draft 0.2, commit f3914f0; entry id symmetric-matrix, kind concept. |
| Status | no ledger row names this entry. Corrections: none recorded. |
| Defining equation | Book equation L.14. |
| Assumptions and scope | none |
| Prior art | none recorded |
| Evidence | none |
| Reviewed | semantic review 2026-09-09; generated 2026-09-10 from records at the commits on the provenance page. |
Equation
Book equation L.14.
\[A=\sum_{i=1}^{d}\lambda_i\,v_iv_i^{\top}=V\Lambda V^{\top},\qquad V^{\top}V=I,\qquad \Lambda=\operatorname{diag}(\lambda_1,\dots,\lambda_d).\]
Conditions
none
Ledger
none
First stated
Primer L section L.3 of Data Mining as Observation, added in draft 0.3 (2026-09-09) for the ECE 514 readers whose first courses are far behind. The idea is standard and TSK Appendix A covers it at length.
Measurements
none
Failures and corrections
none
Invariance envelope
none declared
Machine checked
none
Used in
Data Mining as Observation primers L and S, chapters 0, 3, 4, 5, 9, 10.
Related
transpose; eigenvalue, eigenvector; spectral decomposition; covariance matrix.
See also
none
Status
Generated 2026-09-10 by encyclopedia/generate.py; book
at observation-data-mining f3914f0; the commit of every record is listed
in the encyclopedia’s provenance.