positive definite concept
| Definition | A symmetric matrix whose quadratic form is positive for every nonzero vector, which is the same as every eigenvalue being positive. Positive semidefinite allows zero. Primer L section L.6. |
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| Example | Rows (2, 1) and (1, 2) have eigenvalues 3 and 1 and are positive definite, while rows (1, 2) and (2, 1) give -2 at (1, -1) and are not. |
| Book | Data Mining as Observation, draft 0.2, commit f3914f0; entry id positive-definite, kind concept. |
| Status | no ledger row names this entry. Corrections: none recorded. |
| Defining equation | none |
| 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
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Conditions
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Ledger
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First stated
Primer L section L.6 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
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Failures and corrections
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Invariance envelope
none declared
Machine checked
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Used in
Data Mining as Observation primer L.
Related
positive semidefinite; quadratic form; eigenvalue, eigenvector.
See also
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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.