Partition/Diagram Algebras¶

class sage.combinat.partition_algebra.PartitionAlgebraElement_ak[source]¶: Bases: PartitionAlgebraElement_generic

class sage.combinat.partition_algebra.PartitionAlgebraElement_bk[source]¶: Bases: PartitionAlgebraElement_generic

class sage.combinat.partition_algebra.PartitionAlgebraElement_generic[source]¶: Bases: IndexedFreeModuleElement

class sage.combinat.partition_algebra.PartitionAlgebraElement_pk[source]¶: Bases: PartitionAlgebraElement_generic

class sage.combinat.partition_algebra.PartitionAlgebraElement_prk[source]¶: Bases: PartitionAlgebraElement_generic

class sage.combinat.partition_algebra.PartitionAlgebraElement_rk[source]¶: Bases: PartitionAlgebraElement_generic

class sage.combinat.partition_algebra.PartitionAlgebraElement_sk[source]¶: Bases: PartitionAlgebraElement_generic

class sage.combinat.partition_algebra.PartitionAlgebraElement_tk[source]¶: Bases: PartitionAlgebraElement_generic

class sage.combinat.partition_algebra.PartitionAlgebra_ak(R, k, n, name=None)[source]¶

Bases: PartitionAlgebra_generic

EXAMPLES:

Sage

sage: from sage.combinat.partition_algebra import *
sage: p = PartitionAlgebra_ak(QQ, 3, 1)
sage: p == loads(dumps(p))
True

Python

>>> from sage.all import *
>>> from sage.combinat.partition_algebra import *
>>> p = PartitionAlgebra_ak(QQ, Integer(3), Integer(1))
>>> p == loads(dumps(p))
True

class sage.combinat.partition_algebra.PartitionAlgebra_bk(R, k, n, name=None)[source]¶

Bases: PartitionAlgebra_generic

EXAMPLES:

Sage

sage: from sage.combinat.partition_algebra import *
sage: p = PartitionAlgebra_bk(QQ, 3, 1)
sage: p == loads(dumps(p))
True

Python

>>> from sage.all import *
>>> from sage.combinat.partition_algebra import *
>>> p = PartitionAlgebra_bk(QQ, Integer(3), Integer(1))
>>> p == loads(dumps(p))
True

class sage.combinat.partition_algebra.PartitionAlgebra_generic(R, cclass, n, k, name=None, prefix=None)[source]¶

Bases: CombinatorialFreeModule

EXAMPLES:

Sage

sage: from sage.combinat.partition_algebra import *
sage: s = PartitionAlgebra_sk(QQ, 3, 1)
sage: TestSuite(s).run()
sage: s == loads(dumps(s))
True

Python

>>> from sage.all import *
>>> from sage.combinat.partition_algebra import *
>>> s = PartitionAlgebra_sk(QQ, Integer(3), Integer(1))
>>> TestSuite(s).run()
>>> s == loads(dumps(s))
True

one_basis()[source]¶

Return the basis index for the unit of the algebra.

EXAMPLES:

Sage

sage: from sage.combinat.partition_algebra import *
sage: s = PartitionAlgebra_sk(ZZ, 3, 1)
sage: len(s.one().support())   # indirect doctest
1

Python

>>> from sage.all import *
>>> from sage.combinat.partition_algebra import *
>>> s = PartitionAlgebra_sk(ZZ, Integer(3), Integer(1))
>>> len(s.one().support())   # indirect doctest
1

product_on_basis(left, right)[source]¶

EXAMPLES:

Sage

sage: from sage.combinat.partition_algebra import *
sage: s = PartitionAlgebra_sk(QQ, 3, 1)
sage: t12 = s(Set([Set([1,-2]),Set([2,-1]),Set([3,-3])]))
sage: t12^2 == s(1) #indirect doctest
True

Python

>>> from sage.all import *
>>> from sage.combinat.partition_algebra import *
>>> s = PartitionAlgebra_sk(QQ, Integer(3), Integer(1))
>>> t12 = s(Set([Set([Integer(1),-Integer(2)]),Set([Integer(2),-Integer(1)]),Set([Integer(3),-Integer(3)])]))
>>> t12**Integer(2) == s(Integer(1)) #indirect doctest
True

class sage.combinat.partition_algebra.PartitionAlgebra_pk(R, k, n, name=None)[source]¶

Bases: PartitionAlgebra_generic

EXAMPLES:

Sage

sage: from sage.combinat.partition_algebra import *
sage: p = PartitionAlgebra_pk(QQ, 3, 1)
sage: p == loads(dumps(p))
True

Python

>>> from sage.all import *
>>> from sage.combinat.partition_algebra import *
>>> p = PartitionAlgebra_pk(QQ, Integer(3), Integer(1))
>>> p == loads(dumps(p))
True

class sage.combinat.partition_algebra.PartitionAlgebra_prk(R, k, n, name=None)[source]¶

Bases: PartitionAlgebra_generic

EXAMPLES:

Sage

sage: from sage.combinat.partition_algebra import *
sage: p = PartitionAlgebra_prk(QQ, 3, 1)
sage: p == loads(dumps(p))
True

Python

>>> from sage.all import *
>>> from sage.combinat.partition_algebra import *
>>> p = PartitionAlgebra_prk(QQ, Integer(3), Integer(1))
>>> p == loads(dumps(p))
True

class sage.combinat.partition_algebra.PartitionAlgebra_rk(R, k, n, name=None)[source]¶

Bases: PartitionAlgebra_generic

EXAMPLES:

Sage

sage: from sage.combinat.partition_algebra import *
sage: p = PartitionAlgebra_rk(QQ, 3, 1)
sage: p == loads(dumps(p))
True

Python

>>> from sage.all import *
>>> from sage.combinat.partition_algebra import *
>>> p = PartitionAlgebra_rk(QQ, Integer(3), Integer(1))
>>> p == loads(dumps(p))
True

class sage.combinat.partition_algebra.PartitionAlgebra_sk(R, k, n, name=None)[source]¶

Bases: PartitionAlgebra_generic

EXAMPLES:

Sage

sage: from sage.combinat.partition_algebra import *
sage: p = PartitionAlgebra_sk(QQ, 3, 1)
sage: p == loads(dumps(p))
True

Python

>>> from sage.all import *
>>> from sage.combinat.partition_algebra import *
>>> p = PartitionAlgebra_sk(QQ, Integer(3), Integer(1))
>>> p == loads(dumps(p))
True

class sage.combinat.partition_algebra.PartitionAlgebra_tk(R, k, n, name=None)[source]¶

Bases: PartitionAlgebra_generic

EXAMPLES:

Sage

sage: from sage.combinat.partition_algebra import *
sage: p = PartitionAlgebra_tk(QQ, 3, 1)
sage: p == loads(dumps(p))
True

Python

>>> from sage.all import *
>>> from sage.combinat.partition_algebra import *
>>> p = PartitionAlgebra_tk(QQ, Integer(3), Integer(1))
>>> p == loads(dumps(p))
True

sage.combinat.partition_algebra.SetPartitionsAk(k)[source]¶

Return the combinatorial class of set partitions of type \(A_k\).

EXAMPLES:

Sage

sage: A3 = SetPartitionsAk(3); A3
Set partitions of {1, ..., 3, -1, ..., -3}

sage: A3.first() #random
{{1, 2, 3, -1, -3, -2}}
sage: A3.last() #random
{{-1}, {-2}, {3}, {1}, {-3}, {2}}
sage: A3.random_element()  #random
{{1, 3, -3, -1}, {2, -2}}

sage: A3.cardinality()
203

sage: A2p5 = SetPartitionsAk(2.5); A2p5
Set partitions of {1, ..., 3, -1, ..., -3} with 3 and -3 in the same block
sage: A2p5.cardinality()
52

sage: A2p5.first() #random
{{1, 2, 3, -1, -3, -2}}
sage: A2p5.last() #random
{{-1}, {-2}, {2}, {3, -3}, {1}}
sage: A2p5.random_element() #random
{{-1}, {-2}, {3, -3}, {1, 2}}

Python

>>> from sage.all import *
>>> A3 = SetPartitionsAk(Integer(3)); A3
Set partitions of {1, ..., 3, -1, ..., -3}

>>> A3.first() #random
{{1, 2, 3, -1, -3, -2}}
>>> A3.last() #random
{{-1}, {-2}, {3}, {1}, {-3}, {2}}
>>> A3.random_element()  #random
{{1, 3, -3, -1}, {2, -2}}

>>> A3.cardinality()
203

>>> A2p5 = SetPartitionsAk(RealNumber('2.5')); A2p5
Set partitions of {1, ..., 3, -1, ..., -3} with 3 and -3 in the same block
>>> A2p5.cardinality()
52

>>> A2p5.first() #random
{{1, 2, 3, -1, -3, -2}}
>>> A2p5.last() #random
{{-1}, {-2}, {2}, {3, -3}, {1}}
>>> A2p5.random_element() #random
{{-1}, {-2}, {3, -3}, {1, 2}}

class sage.combinat.partition_algebra.SetPartitionsAk_k(k)[source]¶

Bases: SetPartitions_set

Element[source]¶: alias of SetPartitionsXkElement

class sage.combinat.partition_algebra.SetPartitionsAkhalf_k(k)[source]¶

Bases: SetPartitions_set

Element[source]¶: alias of SetPartitionsXkElement

sage.combinat.partition_algebra.SetPartitionsBk(k)[source]¶

Return the combinatorial class of set partitions of type \(B_k\).

These are the set partitions where every block has size 2.

EXAMPLES:

Sage

sage: B3 = SetPartitionsBk(3); B3
Set partitions of {1, ..., 3, -1, ..., -3} with block size 2

sage: B3.first() #random
{{2, -2}, {1, -3}, {3, -1}}
sage: B3.last() #random
{{1, 2}, {3, -2}, {-3, -1}}
sage: B3.random_element() #random
{{2, -1}, {1, -3}, {3, -2}}

sage: B3.cardinality()
15

sage: B2p5 = SetPartitionsBk(2.5); B2p5
Set partitions of {1, ..., 3, -1, ..., -3} with 3 and -3 in the same block and with block size 2

sage: B2p5.first() #random
{{2, -1}, {3, -3}, {1, -2}}
sage: B2p5.last() #random
{{1, 2}, {3, -3}, {-1, -2}}
sage: B2p5.random_element() #random
{{2, -2}, {3, -3}, {1, -1}}

sage: B2p5.cardinality()
3

Python

>>> from sage.all import *
>>> B3 = SetPartitionsBk(Integer(3)); B3
Set partitions of {1, ..., 3, -1, ..., -3} with block size 2

>>> B3.first() #random
{{2, -2}, {1, -3}, {3, -1}}
>>> B3.last() #random
{{1, 2}, {3, -2}, {-3, -1}}
>>> B3.random_element() #random
{{2, -1}, {1, -3}, {3, -2}}

>>> B3.cardinality()
15

>>> B2p5 = SetPartitionsBk(RealNumber('2.5')); B2p5
Set partitions of {1, ..., 3, -1, ..., -3} with 3 and -3 in the same block and with block size 2

>>> B2p5.first() #random
{{2, -1}, {3, -3}, {1, -2}}
>>> B2p5.last() #random
{{1, 2}, {3, -3}, {-1, -2}}
>>> B2p5.random_element() #random
{{2, -2}, {3, -3}, {1, -1}}

>>> B2p5.cardinality()
3

class sage.combinat.partition_algebra.SetPartitionsBk_k(k)[source]¶

Bases: SetPartitionsAk_k

cardinality()[source]¶

Return the number of set partitions in \(B_k\) where \(k\) is an integer.

This is given by (2k)!! = (2k-1)*(2k-3)*…*5*3*1.

EXAMPLES:

Sage

sage: SetPartitionsBk(3).cardinality()
15
sage: SetPartitionsBk(2).cardinality()
3
sage: SetPartitionsBk(1).cardinality()
1
sage: SetPartitionsBk(4).cardinality()
105
sage: SetPartitionsBk(5).cardinality()
945

Python

>>> from sage.all import *
>>> SetPartitionsBk(Integer(3)).cardinality()
15
>>> SetPartitionsBk(Integer(2)).cardinality()
3
>>> SetPartitionsBk(Integer(1)).cardinality()
1
>>> SetPartitionsBk(Integer(4)).cardinality()
105
>>> SetPartitionsBk(Integer(5)).cardinality()
945

class sage.combinat.partition_algebra.SetPartitionsBkhalf_k(k)[source]¶

Bases: SetPartitionsAkhalf_k

cardinality()[source]¶

sage.combinat.partition_algebra.SetPartitionsIk(k)[source]¶

Return the combinatorial class of set partitions of type \(I_k\).

These are set partitions with a propagating number of less than \(k\). Note that the identity set partition \(\{\{1, -1\}, \ldots, \{k, -k\}\}\) is not in \(I_k\).

EXAMPLES:

Sage

sage: I3 = SetPartitionsIk(3); I3
Set partitions of {1, ..., 3, -1, ..., -3} with propagating number < 3
sage: I3.cardinality()
197

sage: I3.first() #random
{{1, 2, 3, -1, -3, -2}}
sage: I3.last() #random
{{-1}, {-2}, {3}, {1}, {-3}, {2}}
sage: I3.random_element() #random
{{-1}, {-3, -2}, {2, 3}, {1}}

sage: I2p5 = SetPartitionsIk(2.5); I2p5
Set partitions of {1, ..., 3, -1, ..., -3} with 3 and -3 in the same block and propagating number < 3
sage: I2p5.cardinality()
50

sage: I2p5.first() #random
{{1, 2, 3, -1, -3, -2}}
sage: I2p5.last() #random
{{-1}, {-2}, {2}, {3, -3}, {1}}
sage: I2p5.random_element() #random
{{-1}, {-2}, {1, 3, -3}, {2}}

Python

>>> from sage.all import *
>>> I3 = SetPartitionsIk(Integer(3)); I3
Set partitions of {1, ..., 3, -1, ..., -3} with propagating number < 3
>>> I3.cardinality()
197

>>> I3.first() #random
{{1, 2, 3, -1, -3, -2}}
>>> I3.last() #random
{{-1}, {-2}, {3}, {1}, {-3}, {2}}
>>> I3.random_element() #random
{{-1}, {-3, -2}, {2, 3}, {1}}

>>> I2p5 = SetPartitionsIk(RealNumber('2.5')); I2p5
Set partitions of {1, ..., 3, -1, ..., -3} with 3 and -3 in the same block and propagating number < 3
>>> I2p5.cardinality()
50

>>> I2p5.first() #random
{{1, 2, 3, -1, -3, -2}}
>>> I2p5.last() #random
{{-1}, {-2}, {2}, {3, -3}, {1}}
>>> I2p5.random_element() #random
{{-1}, {-2}, {1, 3, -3}, {2}}

class sage.combinat.partition_algebra.SetPartitionsIk_k(k)[source]¶

Bases: SetPartitionsAk_k

cardinality()[source]¶

class sage.combinat.partition_algebra.SetPartitionsIkhalf_k(k)[source]¶

Bases: SetPartitionsAkhalf_k

cardinality()[source]¶

sage.combinat.partition_algebra.SetPartitionsPRk(k)[source]¶

Return the combinatorial class of set partitions of type \(PR_k\).

EXAMPLES:

Sage

sage: SetPartitionsPRk(3)
Set partitions of {1, ..., 3, -1, ..., -3} with at most 1 positive
 and negative entry in each block and that are planar

Python

>>> from sage.all import *
>>> SetPartitionsPRk(Integer(3))
Set partitions of {1, ..., 3, -1, ..., -3} with at most 1 positive
 and negative entry in each block and that are planar

class sage.combinat.partition_algebra.SetPartitionsPRk_k(k)[source]¶

Bases: SetPartitionsRk_k

cardinality()[source]¶

class sage.combinat.partition_algebra.SetPartitionsPRkhalf_k(k)[source]¶

Bases: SetPartitionsRkhalf_k

cardinality()[source]¶

sage.combinat.partition_algebra.SetPartitionsPk(k)[source]¶

Return the combinatorial class of set partitions of type \(P_k\).

These are the planar set partitions.

EXAMPLES:

Sage

sage: P3 = SetPartitionsPk(3); P3
Set partitions of {1, ..., 3, -1, ..., -3} that are planar
sage: P3.cardinality()
132

sage: P3.first() #random
{{1, 2, 3, -1, -3, -2}}
sage: P3.last() #random
{{-1}, {-2}, {3}, {1}, {-3}, {2}}
sage: P3.random_element() #random
{{1, 2, -1}, {-3}, {3, -2}}

sage: P2p5 = SetPartitionsPk(2.5); P2p5
Set partitions of {1, ..., 3, -1, ..., -3} with 3 and -3 in the same block and that are planar
sage: P2p5.cardinality()
42

sage: P2p5.first() #random
{{1, 2, 3, -1, -3, -2}}
sage: P2p5.last() #random
{{-1}, {-2}, {2}, {3, -3}, {1}}
sage: P2p5.random_element() #random
{{1, 2, 3, -3}, {-1, -2}}

Python

>>> from sage.all import *
>>> P3 = SetPartitionsPk(Integer(3)); P3
Set partitions of {1, ..., 3, -1, ..., -3} that are planar
>>> P3.cardinality()
132

>>> P3.first() #random
{{1, 2, 3, -1, -3, -2}}
>>> P3.last() #random
{{-1}, {-2}, {3}, {1}, {-3}, {2}}
>>> P3.random_element() #random
{{1, 2, -1}, {-3}, {3, -2}}

>>> P2p5 = SetPartitionsPk(RealNumber('2.5')); P2p5
Set partitions of {1, ..., 3, -1, ..., -3} with 3 and -3 in the same block and that are planar
>>> P2p5.cardinality()
42

>>> P2p5.first() #random
{{1, 2, 3, -1, -3, -2}}
>>> P2p5.last() #random
{{-1}, {-2}, {2}, {3, -3}, {1}}
>>> P2p5.random_element() #random
{{1, 2, 3, -3}, {-1, -2}}

class sage.combinat.partition_algebra.SetPartitionsPk_k(k)[source]¶

Bases: SetPartitionsAk_k

cardinality()[source]¶

class sage.combinat.partition_algebra.SetPartitionsPkhalf_k(k)[source]¶

Bases: SetPartitionsAkhalf_k

cardinality()[source]¶

sage.combinat.partition_algebra.SetPartitionsRk(k)[source]¶

Return the combinatorial class of set partitions of type \(R_k\).

EXAMPLES:

Sage

sage: SetPartitionsRk(3)
Set partitions of {1, ..., 3, -1, ..., -3} with at most 1 positive
 and negative entry in each block

Python

>>> from sage.all import *
>>> SetPartitionsRk(Integer(3))
Set partitions of {1, ..., 3, -1, ..., -3} with at most 1 positive
 and negative entry in each block

class sage.combinat.partition_algebra.SetPartitionsRk_k(k)[source]¶

Bases: SetPartitionsAk_k

cardinality()[source]¶

class sage.combinat.partition_algebra.SetPartitionsRkhalf_k(k)[source]¶

Bases: SetPartitionsAkhalf_k

cardinality()[source]¶

sage.combinat.partition_algebra.SetPartitionsSk(k)[source]¶

Return the combinatorial class of set partitions of type \(S_k\).

There is a bijection between these set partitions and the permutations of \(1, \ldots, k\).

EXAMPLES:

Sage

sage: S3 = SetPartitionsSk(3); S3
Set partitions of {1, ..., 3, -1, ..., -3} with propagating number 3
sage: S3.cardinality()
6

sage: S3.list()  #random
[{{2, -2}, {3, -3}, {1, -1}},
 {{1, -1}, {2, -3}, {3, -2}},
 {{2, -1}, {3, -3}, {1, -2}},
 {{1, -2}, {2, -3}, {3, -1}},
 {{1, -3}, {2, -1}, {3, -2}},
 {{1, -3}, {2, -2}, {3, -1}}]
sage: S3.first() #random
{{2, -2}, {3, -3}, {1, -1}}
sage: S3.last() #random
{{1, -3}, {2, -2}, {3, -1}}
sage: S3.random_element() #random
{{1, -3}, {2, -1}, {3, -2}}

sage: S3p5 = SetPartitionsSk(3.5); S3p5
Set partitions of {1, ..., 4, -1, ..., -4} with 4 and -4 in the same block and propagating number 4
sage: S3p5.cardinality()
6

sage: S3p5.list() #random
[{{2, -2}, {3, -3}, {1, -1}, {4, -4}},
 {{2, -3}, {1, -1}, {4, -4}, {3, -2}},
 {{2, -1}, {3, -3}, {1, -2}, {4, -4}},
 {{2, -3}, {1, -2}, {4, -4}, {3, -1}},
 {{1, -3}, {2, -1}, {4, -4}, {3, -2}},
 {{1, -3}, {2, -2}, {4, -4}, {3, -1}}]
sage: S3p5.first() #random
{{2, -2}, {3, -3}, {1, -1}, {4, -4}}
sage: S3p5.last() #random
{{1, -3}, {2, -2}, {4, -4}, {3, -1}}
sage: S3p5.random_element() #random
{{1, -3}, {2, -2}, {4, -4}, {3, -1}}

Python

>>> from sage.all import *
>>> S3 = SetPartitionsSk(Integer(3)); S3
Set partitions of {1, ..., 3, -1, ..., -3} with propagating number 3
>>> S3.cardinality()
6

>>> S3.list()  #random
[{{2, -2}, {3, -3}, {1, -1}},
 {{1, -1}, {2, -3}, {3, -2}},
 {{2, -1}, {3, -3}, {1, -2}},
 {{1, -2}, {2, -3}, {3, -1}},
 {{1, -3}, {2, -1}, {3, -2}},
 {{1, -3}, {2, -2}, {3, -1}}]
>>> S3.first() #random
{{2, -2}, {3, -3}, {1, -1}}
>>> S3.last() #random
{{1, -3}, {2, -2}, {3, -1}}
>>> S3.random_element() #random
{{1, -3}, {2, -1}, {3, -2}}

>>> S3p5 = SetPartitionsSk(RealNumber('3.5')); S3p5
Set partitions of {1, ..., 4, -1, ..., -4} with 4 and -4 in the same block and propagating number 4
>>> S3p5.cardinality()
6

>>> S3p5.list() #random
[{{2, -2}, {3, -3}, {1, -1}, {4, -4}},
 {{2, -3}, {1, -1}, {4, -4}, {3, -2}},
 {{2, -1}, {3, -3}, {1, -2}, {4, -4}},
 {{2, -3}, {1, -2}, {4, -4}, {3, -1}},
 {{1, -3}, {2, -1}, {4, -4}, {3, -2}},
 {{1, -3}, {2, -2}, {4, -4}, {3, -1}}]
>>> S3p5.first() #random
{{2, -2}, {3, -3}, {1, -1}, {4, -4}}
>>> S3p5.last() #random
{{1, -3}, {2, -2}, {4, -4}, {3, -1}}
>>> S3p5.random_element() #random
{{1, -3}, {2, -2}, {4, -4}, {3, -1}}

class sage.combinat.partition_algebra.SetPartitionsSk_k(k)[source]¶

Bases: SetPartitionsAk_k

cardinality()[source]¶: Return k!.

class sage.combinat.partition_algebra.SetPartitionsSkhalf_k(k)[source]¶

Bases: SetPartitionsAkhalf_k

cardinality()[source]¶

sage.combinat.partition_algebra.SetPartitionsTk(k)[source]¶

Return the combinatorial class of set partitions of type \(T_k\).

These are planar set partitions where every block is of size 2.

EXAMPLES:

Sage

sage: T3 = SetPartitionsTk(3); T3
Set partitions of {1, ..., 3, -1, ..., -3} with block size 2 and that are planar
sage: T3.cardinality()
5

sage: T3.first() #random
{{1, -3}, {2, 3}, {-1, -2}}
sage: T3.last() #random
{{1, 2}, {3, -1}, {-3, -2}}
sage: T3.random_element() #random
{{1, -3}, {2, 3}, {-1, -2}}

sage: T2p5 = SetPartitionsTk(2.5); T2p5
Set partitions of {1, ..., 3, -1, ..., -3} with 3 and -3 in the same block and with block size 2 and that are planar
sage: T2p5.cardinality()
2

sage: T2p5.first() #random
{{2, -2}, {3, -3}, {1, -1}}
sage: T2p5.last() #random
{{1, 2}, {3, -3}, {-1, -2}}

Python

>>> from sage.all import *
>>> T3 = SetPartitionsTk(Integer(3)); T3
Set partitions of {1, ..., 3, -1, ..., -3} with block size 2 and that are planar
>>> T3.cardinality()
5

>>> T3.first() #random
{{1, -3}, {2, 3}, {-1, -2}}
>>> T3.last() #random
{{1, 2}, {3, -1}, {-3, -2}}
>>> T3.random_element() #random
{{1, -3}, {2, 3}, {-1, -2}}

>>> T2p5 = SetPartitionsTk(RealNumber('2.5')); T2p5
Set partitions of {1, ..., 3, -1, ..., -3} with 3 and -3 in the same block and with block size 2 and that are planar
>>> T2p5.cardinality()
2

>>> T2p5.first() #random
{{2, -2}, {3, -3}, {1, -1}}
>>> T2p5.last() #random
{{1, 2}, {3, -3}, {-1, -2}}

class sage.combinat.partition_algebra.SetPartitionsTk_k(k)[source]¶

Bases: SetPartitionsBk_k

cardinality()[source]¶

class sage.combinat.partition_algebra.SetPartitionsTkhalf_k(k)[source]¶

Bases: SetPartitionsBkhalf_k

cardinality()[source]¶

class sage.combinat.partition_algebra.SetPartitionsXkElement(parent, s, check=True)[source]¶

Bases: SetPartition

An element for the classes of SetPartitionXk where X is some letter.

check()[source]¶

Check to make sure this is a set partition.

EXAMPLES:

Sage

sage: A2p5 = SetPartitionsAk(2.5)
sage: x = A2p5.first(); x
{{-3, -2, -1, 1, 2, 3}}
sage: x.check()
sage: y = A2p5.next(x); y
{{-3, 3}, {-2, -1, 1, 2}}
sage: y.check()

Python

>>> from sage.all import *
>>> A2p5 = SetPartitionsAk(RealNumber('2.5'))
>>> x = A2p5.first(); x
{{-3, -2, -1, 1, 2, 3}}
>>> x.check()
>>> y = A2p5.next(x); y
{{-3, 3}, {-2, -1, 1, 2}}
>>> y.check()

sage.combinat.partition_algebra.identity(k)[source]¶

Return the identity set partition \(1, -1, \ldots, k, -k\).

EXAMPLES:

Sage

sage: import sage.combinat.partition_algebra as pa
sage: pa.identity(2)
{{2, -2}, {1, -1}}

Python

>>> from sage.all import *
>>> import sage.combinat.partition_algebra as pa
>>> pa.identity(Integer(2))
{{2, -2}, {1, -1}}

sage.combinat.partition_algebra.is_planar(sp)[source]¶

Return True if the diagram corresponding to the set partition is planar; otherwise, it returns False.

EXAMPLES:

Sage

sage: import sage.combinat.partition_algebra as pa
sage: pa.is_planar( pa.to_set_partition([[1,-2],[2,-1]]))
False
sage: pa.is_planar( pa.to_set_partition([[1,-1],[2,-2]]))
True

Python

>>> from sage.all import *
>>> import sage.combinat.partition_algebra as pa
>>> pa.is_planar( pa.to_set_partition([[Integer(1),-Integer(2)],[Integer(2),-Integer(1)]]))
False
>>> pa.is_planar( pa.to_set_partition([[Integer(1),-Integer(1)],[Integer(2),-Integer(2)]]))
True

sage.combinat.partition_algebra.pair_to_graph(sp1, sp2)[source]¶

Return a graph consisting of the disjoint union of the graphs of set partitions sp1 and sp2 along with edges joining the bottom row (negative numbers) of sp1 to the top row (positive numbers) of sp2.

The vertices of the graph sp1 appear in the result as pairs (k, 1), whereas the vertices of the graph sp2 appear as pairs (k, 2).

EXAMPLES:

Sage

sage: import sage.combinat.partition_algebra as pa
sage: sp1 = pa.to_set_partition([[1,-2],[2,-1]])
sage: sp2 = pa.to_set_partition([[1,-2],[2,-1]])
sage: g = pa.pair_to_graph( sp1, sp2 ); g
Graph on 8 vertices

Python

>>> from sage.all import *
>>> import sage.combinat.partition_algebra as pa
>>> sp1 = pa.to_set_partition([[Integer(1),-Integer(2)],[Integer(2),-Integer(1)]])
>>> sp2 = pa.to_set_partition([[Integer(1),-Integer(2)],[Integer(2),-Integer(1)]])
>>> g = pa.pair_to_graph( sp1, sp2 ); g
Graph on 8 vertices

Sage

sage: g.vertices(sort=False) #random
[(1, 2), (-1, 1), (-2, 2), (-1, 2), (-2, 1), (2, 1), (2, 2), (1, 1)]
sage: g.edges(sort=False) #random
[((1, 2), (-1, 1), None),
 ((1, 2), (-2, 2), None),
 ((-1, 1), (2, 1), None),
 ((-1, 2), (2, 2), None),
 ((-2, 1), (1, 1), None),
 ((-2, 1), (2, 2), None)]

Python

>>> from sage.all import *
>>> g.vertices(sort=False) #random
[(1, 2), (-1, 1), (-2, 2), (-1, 2), (-2, 1), (2, 1), (2, 2), (1, 1)]
>>> g.edges(sort=False) #random
[((1, 2), (-1, 1), None),
 ((1, 2), (-2, 2), None),
 ((-1, 1), (2, 1), None),
 ((-1, 2), (2, 2), None),
 ((-2, 1), (1, 1), None),
 ((-2, 1), (2, 2), None)]

Another example which used to be wrong until Issue #15958:

Sage

sage: sp3 = pa.to_set_partition([[1, -1], [2], [-2]])
sage: sp4 = pa.to_set_partition([[1], [-1], [2], [-2]])
sage: g = pa.pair_to_graph( sp3, sp4 ); g
Graph on 8 vertices

sage: g.vertices(sort=True)
[(-2, 1), (-2, 2), (-1, 1), (-1, 2), (1, 1), (1, 2), (2, 1), (2, 2)]
sage: g.edges(sort=True)
[((-2, 1), (2, 2), None), ((-1, 1), (1, 1), None),
 ((-1, 1), (1, 2), None)]

Python

>>> from sage.all import *
>>> sp3 = pa.to_set_partition([[Integer(1), -Integer(1)], [Integer(2)], [-Integer(2)]])
>>> sp4 = pa.to_set_partition([[Integer(1)], [-Integer(1)], [Integer(2)], [-Integer(2)]])
>>> g = pa.pair_to_graph( sp3, sp4 ); g
Graph on 8 vertices

>>> g.vertices(sort=True)
[(-2, 1), (-2, 2), (-1, 1), (-1, 2), (1, 1), (1, 2), (2, 1), (2, 2)]
>>> g.edges(sort=True)
[((-2, 1), (2, 2), None), ((-1, 1), (1, 1), None),
 ((-1, 1), (1, 2), None)]

sage.combinat.partition_algebra.propagating_number(sp)[source]¶

Return the propagating number of the set partition sp.

The propagating number is the number of blocks with both a positive and negative number.

EXAMPLES:

Sage

sage: import sage.combinat.partition_algebra as pa
sage: sp1 = pa.to_set_partition([[1,-2],[2,-1]])
sage: sp2 = pa.to_set_partition([[1,2],[-2,-1]])
sage: pa.propagating_number(sp1)
2
sage: pa.propagating_number(sp2)
0

Python

>>> from sage.all import *
>>> import sage.combinat.partition_algebra as pa
>>> sp1 = pa.to_set_partition([[Integer(1),-Integer(2)],[Integer(2),-Integer(1)]])
>>> sp2 = pa.to_set_partition([[Integer(1),Integer(2)],[-Integer(2),-Integer(1)]])
>>> pa.propagating_number(sp1)
2
>>> pa.propagating_number(sp2)
0

sage.combinat.partition_algebra.set_partition_composition(sp1, sp2)[source]¶

Return a tuple consisting of the composition of the set partitions sp1 and sp2 and the number of components removed from the middle rows of the graph.

EXAMPLES:

Sage

sage: import sage.combinat.partition_algebra as pa
sage: sp1 = pa.to_set_partition([[1,-2],[2,-1]])
sage: sp2 = pa.to_set_partition([[1,-2],[2,-1]])
sage: pa.set_partition_composition(sp1, sp2) == (pa.identity(2), 0)
True

Python

>>> from sage.all import *
>>> import sage.combinat.partition_algebra as pa
>>> sp1 = pa.to_set_partition([[Integer(1),-Integer(2)],[Integer(2),-Integer(1)]])
>>> sp2 = pa.to_set_partition([[Integer(1),-Integer(2)],[Integer(2),-Integer(1)]])
>>> pa.set_partition_composition(sp1, sp2) == (pa.identity(Integer(2)), Integer(0))
True

sage.combinat.partition_algebra.to_graph(sp)[source]¶

Return a graph representing the set partition sp.

EXAMPLES:

Sage

sage: import sage.combinat.partition_algebra as pa
sage: g = pa.to_graph( pa.to_set_partition([[1,-2],[2,-1]])); g
Graph on 4 vertices

sage: g.vertices(sort=False) #random
[1, 2, -2, -1]
sage: g.edges(sort=False) #random
[(1, -2, None), (2, -1, None)]

Python

>>> from sage.all import *
>>> import sage.combinat.partition_algebra as pa
>>> g = pa.to_graph( pa.to_set_partition([[Integer(1),-Integer(2)],[Integer(2),-Integer(1)]])); g
Graph on 4 vertices

>>> g.vertices(sort=False) #random
[1, 2, -2, -1]
>>> g.edges(sort=False) #random
[(1, -2, None), (2, -1, None)]

sage.combinat.partition_algebra.to_set_partition(l, k=None)[source]¶

Convert a list of a list of numbers to a set partitions.

Each list of numbers in the outer list specifies the numbers contained in one of the blocks in the set partition.

If k is specified, then the set partition will be a set partition of 1, …, k, -1, …, -k. Otherwise, k will default to the minimum number needed to contain all of the specified numbers.

EXAMPLES:

Sage

sage: import sage.combinat.partition_algebra as pa
sage: pa.to_set_partition([[1,-1],[2,-2]]) == pa.identity(2)
True

Python

>>> from sage.all import *
>>> import sage.combinat.partition_algebra as pa
>>> pa.to_set_partition([[Integer(1),-Integer(1)],[Integer(2),-Integer(2)]]) == pa.identity(Integer(2))
True