Geometry MOC

Incidence relation

Incidence is a relation between geometric subspaces (points, lines, planes, &c.), generalizing the notion of a point being on a line, a line being in a plane, a plane containing a line, &c. In each case the subspaces are said to be incident with one another.

Incidence matrix

Given subspaces (๐‘๐‘–)๐‘›๐‘–=1 of one type and subspaces (โ„“๐‘–)๐‘š๐‘–=1 of another, the incidence relationship between these may be summarized by an ๐‘š ร—๐‘› incidence matrix geo

[I]=โŽกโŽข โŽขโŽฃ[โ„“1I๐‘1]โ‹ฏ[โ„“1I๐‘๐‘›]โ‹ฎโ‹ฑโ‹ฎ[โ„“๐‘šI๐‘1]โ€ฆ[โ„“๐‘šI๐‘๐‘›]โŽคโŽฅ โŽฅโŽฆโˆˆM๐‘šร—๐‘›(๐•‚2)

where we have invoked the Iverson bracket.


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