next | previous | forward | backward | up | top | index | toc | Macaulay2 website
Matroids :: contraction

contraction -- contraction of subset of matroid

Synopsis

Description

The contraction of M by S is given by M/S := (M* \ S)*, where * stands for dual, and \ is deletion.

i1 : M = matroid({a,b,c,d},{{a,b},{a,c}})

o1 = a matroid of rank 2 on 4 elements

o1 : Matroid
i2 : N = M / {c}

o2 = a matroid of rank 1 on 3 elements

o2 : Matroid
i3 : peek N

o3 = Matroid{bases => {set {0}}          }
             cache => CacheTable{...3...}
             groundSet => set {0, 1, 2}
             rank => 1
i4 : N == M / set{2}

o4 = true

See also

Ways to use contraction :

For the programmer

The object contraction is a method function.