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<Chapter><Heading>Basic functionality for cellular complexes, fundamental groups and homology</Heading> This page covers the functions used in chapters 1 and 2 of the book <URL><Link>https://global.oup.com/academic/product/an-invitation-to-computational-homotopy-9780198832980</Link><LinkText>An Invitation to Computational Homotopy</LinkText></URL>. <Section><Heading> Data <M>\longrightarrow</M> Cellular Complexes </Heading>
<ManSection> <Func Name="RegularCWPolytope" Arg="L"/> <Func Name="RegularCWPolytope" Arg="G,v"/> <Description><P/> <P/> Inputs a list <M>L</M> of vectors in <M>\mathbb R^n</M> and outputs their convex hull as a regular CW-complex. <P/> Inputs a permutation group G of degree <M>d</M> and vector <M>v\in \mathbb R^d</M>, and outputs the convex hull of the orbit <M>\{v^g : g\in G\}</M> as a regular CW-complex. <P/><B>Examples:</B>
</Description> </ManSection>
<ManSection> <Func Name="CubicalComplex" Arg="A"/> <Description><P/> <P/> Inputs a binary array <M>A</M> and returns the cubical complex represented by <M>A</M>. The array <M>A</M> must of course be such that it represents a cubical complex. <P/><B>Examples:</B> <URL><Link>../tutorial/chap2.html</Link><LinkText>1</LinkText></URL> , <URL><Link>../tutorial/chap3.html</Link><LinkText>2</LinkText></URL> , <URL><Link>../tutorial/chap5.html</Link><LinkText>3</LinkText></URL> , <URL><Link>../tutorial/chap10.html</Link><LinkText>4</LinkText></URL> , <URL><Link>../www/SideLinks/About/aboutLinks.html</Link><LinkText>5</LinkText></URL> , <URL><Link>../www/SideLinks/About/aboutPersistent.html</Link><LinkText>6</LinkText></URL> , <URL><Link>../www/SideLinks/About/aboutCoveringSpaces.html</Link><LinkText>7</LinkText></URL> , <URL><Link>../www/SideLinks/About/aboutCoverinSpaces.html</Link><LinkText>8</LinkText></URL> , <URL><Link>../www/SideLinks/About/aboutCubical.html</Link><LinkText>9</LinkText></URL> , <URL><Link>../www/SideLinks/About/aboutRandomComplexes.html</Link><LinkText>10</LinkText></URL> , <URL><Link>../www/SideLinks/About/aboutTDA.html</Link><LinkText>11</LinkText></URL> , <URL><Link>../www/SideLinks/About/aboutKnots.html</Link><LinkText>12</LinkText></URL>
</Description> </ManSection>
<ManSection> <Func Name="PureCubicalComplex" Arg="A"/> <Description><P/> <P/> Inputs a binary array <M>A</M> and returns the pure cubical complex represented by <M>A</M>. <P/><B>Examples:</B> <URL><Link>../tutorial/chap2.html</Link><LinkText>1</LinkText></URL> , <URL><Link>../tutorial/chap3.html</Link><LinkText>2</LinkText></URL> , <URL><Link>../tutorial/chap5.html</Link><LinkText>3</LinkText></URL> , <URL><Link>../tutorial/chap10.html</Link><LinkText>4</LinkText></URL> , <URL><Link>../www/SideLinks/About/aboutLinks.html</Link><LinkText>5</LinkText></URL> , <URL><Link>../www/SideLinks/About/aboutPersistent.html</Link><LinkText>6</LinkText></URL> , <URL><Link>../www/SideLinks/About/aboutCoveringSpaces.html</Link><LinkText>7</LinkText></URL> , <URL><Link>../www/SideLinks/About/aboutCoverinSpaces.html</Link><LinkText>8</LinkText></URL> , <URL><Link>../www/SideLinks/About/aboutCubical.html</Link><LinkText>9</LinkText></URL> , <URL><Link>../www/SideLinks/About/aboutRandomComplexes.html</Link><LinkText>10</LinkText></URL> , <URL><Link>../www/SideLinks/About/aboutTDA.html</Link><LinkText>11</LinkText></URL> , <URL><Link>../www/SideLinks/About/aboutKnots.html</Link><LinkText>12</LinkText></URL>
</Description> </ManSection>
<ManSection> <Func Name="PureCubicalKnot" Arg="n,k"/> <Func Name="PureCubicalKnot" Arg="L"/> <Description><P/> <P/> Inputs integers <M>n, k</M> and returns the <M>k</M>-th prime knot on <M>n</M> crossings as a pure cubical complex (if this prime knot exists). <P/> Inputs a list <M>L</M> describing an arc presentation for a knot or link and returns the knot or link as a pure cubical complex. <P/><B>Examples:</B> <URL><Link>../tutorial/chap1.html</Link><LinkText>1</LinkText></URL> , <URL><Link>../tutorial/chap2.html</Link><LinkText>2</LinkText></URL> , <URL><Link>../tutorial/chap3.html</Link><LinkText>3</LinkText></URL> , <URL><Link>../tutorial/chap4.html</Link><LinkText>4</LinkText></URL> , <URL><Link>../tutorial/chap6.html</Link><LinkText>5</LinkText></URL> , <URL><Link>../www/SideLinks/About/aboutCoveringSpaces.html</Link><LinkText>6</LinkText></URL> , <URL><Link>../www/SideLinks/About/aboutCoverinSpaces.html</Link><LinkText>7</LinkText></URL> , <URL><Link>../www/SideLinks/About/aboutQuandles2.html</Link><LinkText>8</LinkText></URL> , <URL><Link>../www/SideLinks/About/aboutQuandles.html</Link><LinkText>9</LinkText></URL> , <URL><Link>../www/SideLinks/About/aboutKnots.html</Link><LinkText>10</LinkText></URL> , <URL><Link>../www/SideLinks/About/aboutKnotsQuandles.html</Link><LinkText>11</LinkText></URL>
</Description> </ManSection>
<ManSection> <Func Name="PurePermutahedralKnot" Arg="n,k"/> <Func Name="PurePermutahedralKnot" Arg="L"/> <Description> <P/> Inputs integers <M>n, k</M> and returns the <M>k</M>-th prime knot on <M>n</M> crossings as a pure permutahedral complex (if this prime knot exists). <P/> Inputs a list <M>L</M> describing an arc presentation for a knot or link and returns the knot or link as a pure permutahedral complex. <P/><B>Examples:</B> <URL><Link>../tutorial/chap1.html</Link><LinkText>1</LinkText></URL> , <URL><Link>../tutorial/chap10.html</Link><LinkText>2</LinkText></URL>
</Description> </ManSection>
<ManSection> <Func Name="PurePermutahedralComplex" Arg="A"/> <Description><P/> <P/> Inputs a binary array <M>A</M> and returns the pure permutahedral complex represented by <M>A</M>. <P/><B>Examples:</B> <URL><Link>../tutorial/chap2.html</Link><LinkText>1</LinkText></URL> , <URL><Link>../tutorial/chap5.html</Link><LinkText>2</LinkText></URL> , <URL><Link>../www/SideLinks/About/aboutPeripheral.html</Link><LinkText>3</LinkText></URL> , <URL><Link>../www/SideLinks/About/aboutCubical.html</Link><LinkText>4</LinkText></URL>
</Description> </ManSection>
<ManSection> <Func Name="CayleyGraphOfGroup" Arg="G,L"/> <Description><P/> <P/> Inputs a finite group <M>G</M> and a list <M>L</M> of elements in <M>G</M>.It returns the Cayley graph of the group generated by <M>L</M>. <P/><B>Examples:</B>
</Description> </ManSection>
<ManSection> <Func Name="EquivariantEuclideanSpace" Arg="G,v"/> <Description><P/> <P/> Inputs a crystallographic group <M>G</M> with left action on <M>\mathbb R^n</M> together with a row vector <M>v \in \mathbb R^n</M>. It returns an equivariant regular CW-space corresponding to the Dirichlet-Voronoi tessellation of <M>\mathbb R^n</M> produced from the orbit of <M>v</M> under the action. <P/><B>Examples:</B> <URL><Link>../tutorial/chap1.html</Link><LinkText>1</LinkText></URL>
</Description> </ManSection>
<ManSection> <Func Name="EquivariantOrbitPolytope" Arg="G,v"/> <Description><P/> <P/> Inputs a permutation group <M>G</M> of degree <M>n</M> together with a row vector <M>v \in \mathbb R^n</M>. It returns, as an equivariant regular CW-space, the convex hull of the orbit of <M>v</M> under the canonical left action of <M>G</M> on <M>\mathbb R^n</M>. <P/><B>Examples:</B>
</Description> </ManSection>
<ManSection> <Func Name="EquivariantTwoComplex" Arg="G"/> <Description><P/> <P/> Inputs a suitable group <M>G</M> and returns, as an equivariant regular CW-space, the <M>2</M>-complex associated to some presentation of <M>G</M>. <P/><B>Examples:</B> <URL><Link>../tutorial/chap1.html</Link><LinkText>1</LinkText></URL>
</Description> </ManSection>
<ManSection> <Func Name="QuillenComplex" Arg="G,p"/> <Description><P/> <P/> Inputs a finite group <M>G</M> and prime <M>p</M>, and returns the simplicial complex arising as the order complex of the poset of elementary abelian <M>p</M>-subgroups of <M>G</M>. <P/><B>Examples:</B> <URL><Link>../tutorial/chap1.html</Link><LinkText>1</LinkText></URL> , <URL><Link>../tutorial/chap10.html</Link><LinkText>2</LinkText></URL> , <URL><Link>../www/SideLinks/About/aboutBredon.html</Link><LinkText>3</LinkText></URL> , <URL><Link>../www/SideLinks/About/aboutCubical.html</Link><LinkText>4</LinkText></URL>
</Description> </ManSection>
<ManSection> <Func Name="RestrictedEquivariantCWComplex" Arg="Y,H"/> <Description><P/> <P/> Inputs a <M>G</M>-equivariant regular CW-space Y and a subgroup <M>H \le G</M> for which GAP can find a transversal. It returns the equivariant regular CW-complex obtained by retricting the action to <M>H</M>. <P/><B>Examples:</B>
</Description> </ManSection>
<ManSection> <Func Name="RandomSimplicialGraph" Arg="n,p"/> <Description><P/> <P/> Inputs an integer <M> n \ge 1 </M> and positive prime <M>p</M>, and returns an Erdős–Rényi random graph as a <M>1</M>-dimensional simplicial complex. The graph has <M>n</M> vertices. Each pair of vertices is, with probability <M>p</M>, directly connected by an edge. <P/><B>Examples:</B> <URL><Link>../www/SideLinks/About/aboutRandomComplexes.html</Link><LinkText>1</LinkText></URL>
</Description> </ManSection>
<ManSection> <Func Name="RandomSimplicialTwoComplex" Arg="n,p"/> <Description><P/> <P/> Inputs an integer <M> n \ge 1 </M> and positive prime <M>p</M>, and returns a Linial-Meshulam random simplicial <M>2</M>-complex. The <M>1</M>-skeleton of this simplicial complex is the complete graph on <M>n</M> vertices. Each triple of vertices lies, with probability <M>p</M>, in a common <M>2</M>-simplex of the complex. <P/><B>Examples:</B> <URL><Link>../tutorial/chap5.html</Link><LinkText>1</LinkText></URL> , <URL><Link>../www/SideLinks/About/aboutRandomComplexes.html</Link><LinkText>2</LinkText></URL>
</Description> </ManSection>
<ManSection> <Func Name="ReadCSVfileAsPureCubicalKnot" Arg="str"/> <Func Name="ReadCSVfileAsPureCubicalKnot" Arg="str,r"/> <Func Name="ReadCSVfileAsPureCubicalKnot" Arg="L"/> <Func Name="ReadCSVfileAsPureCubicalKnot" Arg="L,R"/> <Description><P/> <P/> Reads a CSV file identified by a string str such as "file.pdb" or "path/file.pdb" and returns a <M>3</M>-dimensional pure cubical complex <M>K</M>. Each line of the file should contain the coordinates of a point in <M>\mathbb R^3</M> and the complex <M>K</M> should represent a knot determined by the sequence of points, though the latter is not guaranteed. A useful check in this direction is to test that <M>K</M> has the homotopy type of a circle. <P/>If the test fails then try the function again with an integer <M>r \ge 2</M> entered as the optional second argument. The integer determines the resolution with which the knot is constructed. <P/> The function can also read in a list <M>L</M> of strings identifying CSV files for several knots. In this case a list <M>R</M> of integer resolutions can also be entered. The lists <M>L</M> and <M>R</M> must be of equal length. <P/><B>Examples:</B> <URL><Link>../tutorial/chap2.html</Link><LinkText>1</LinkText></URL>
</Description> </ManSection>
<ManSection> <Func Name="ReadImageAsPureCubicalComplex" Arg="str,t"/> <Description><P/> <P/> Reads an image file identified by a string str such as "file.bmp", "file.eps", "file.jpg", "path/file.png" etc., together with an integer <M>t</M> between <M>0</M> and <M>765</M>. It returns a <M>2</M>-dimensional pure cubical complex corresponding to a black/white version of the image determined by the threshold <M>t</M>. The <M>2</M>-cells of the pure cubical complex correspond to pixels with RGB value <M>R+G+B \le t</M>. <P/><B>Examples:</B> <URL><Link>../tutorial/chap5.html</Link><LinkText>1</LinkText></URL> , <URL><Link>../tutorial/chap10.html</Link><LinkText>2</LinkText></URL> , <URL><Link>../www/SideLinks/About/aboutPersistent.html</Link><LinkText>3</LinkText></URL> , <URL><Link>../www/SideLinks/About/aboutCubical.html</Link><LinkText>4</LinkText></URL> , <URL><Link>../www/SideLinks/About/aboutTDA.html</Link><LinkText>5</LinkText></URL>
</Description> </ManSection>
<ManSection> <Func Name="ReadImageAsFilteredPureCubicalComplex" Arg="str,n"/> <Description><P/> <P/> Reads an image file identified by a string str such as "file.bmp", "file.eps", "file.jpg", "path/file.png" etc., together with a positive integer <M>n</M>. It returns a <M>2</M>-dimensional filtered pure cubical complex of filtration length <M>n</M>. The <M>k</M>th term in the filtration is a pure cubical complex corresponding to a black/white version of the image determined by the threshold <M>t_k=k \times 765/n </M>. The <M>2</M>-cells of the <M>k</M>th term correspond to pixels with RGB value <M>R+G+B \le t_k</M>. <P/><B>Examples:</B> <URL><Link>../tutorial/chap5.html</Link><LinkText>1</LinkText></URL>
</Description> </ManSection>
<ManSection> <Func Name="ReadImageAsWeightFunction" Arg="str,t"/> <Description><P/> <P/> Reads an image file identified by a string str such as "file.bmp", "file.eps", "file.jpg", "path/file.png" etc., together with an integer <M>t</M>. It constructs a <M>2</M>-dimensional regular CW-complex <M>Y</M> from the image, together with a weight function <M>w\colon Y\rightarrow \mathbb Z</M> corresponding to a filtration on <M>Y</M> of filtration length <M>t</M>. The pair <M>[Y,w]</M> is returned. <P/><B>Examples:</B>
</Description> </ManSection>
<ManSection> <Func Name="ReadPDBfileAsPureCubicalComplex" Arg="str"/> <Func Name="ReadPDBfileAsPureCubicalComplex" Arg="str,r"/> <Description><P/> <P/> Reads a PDB (Protein Database) file identified by a string str such as "file.pdb" or "path/file.pdb" and returns a <M>3</M>-dimensional pure cubical complex <M>K</M>. The complex <M>K</M> should represent a (protein backbone) knot but this is not guaranteed. A useful check in this direction is to test that <M>K</M> has the homotopy type of a circle. <P/>If the test fails then try the function again with an integer <M>r \ge 2</M> entered as the optional second argument. The integer determines the resolution with which the knot is constructed. <P/><B>Examples:</B> <URL><Link>../tutorial/chap5.html</Link><LinkText>1</LinkText></URL> , <URL><Link>../www/SideLinks/About/aboutPersistent.html</Link><LinkText>2</LinkText></URL> , <URL><Link>../www/SideLinks/About/aboutKnots.html</Link><LinkText>3</LinkText></URL>
</Description> </ManSection>
<ManSection> <Var Name="ReadPDBfileAsPurepermutahedralComplex"/> <Func Name="ReadPDBfileAsPurePermutahedralComplex" Arg="str,r"/> <Description><P/> <P/> Reads a PDB (Protein Database) file identified by a string str such as "file.pdb" or "path/file.pdb" and returns a <M>3</M>-dimensional pure permutahedral complex <M>K</M>. The complex <M>K</M> should represent a (protein backbone) knot but this is not guaranteed. A useful check in this direction is to test that <M>K</M> has the homotopy type of a circle. <P/>If the test fails then try the function again with an integer <M>r \ge 2</M> entered as the optional second argument. The integer determines the resolution with which the knot is constructed. <P/><B>Examples:</B>
</Description> </ManSection>
<ManSection> <Func Name="RegularCWPolytope" Arg="L"/> <Func Name="RegularCWPolytope" Arg="G,v"/> <Description><P/> <P/> Inputs a list <M>L</M> of vectors in <M>\mathbb R^n</M> and outputs their convex hull as a regular CW-complex. <P/> Inputs a permutation group G of degree <M>d</M> and vector <M>v\in \mathbb R^d</M>, and outputs the convex hull of the orbit <M>\{v^g : g\in G\}</M> as a regular CW-complex. <P/><B>Examples:</B>
</Description> </ManSection>
<ManSection> <Func Name="SimplicialComplex" Arg="L"/> <Description><P/> <P/>Inputs a list <M>L</M> whose entries are lists of vertices representing the maximal simplices of a simplicial complex, and returns the simplicial complex. Here a "vertex" is a GAP object such as an integer or a subgroup. The list <M>L</M> can also contain non-maximal simplices. <P/><B>Examples:</B> <URL><Link>../tutorial/chap1.html</Link><LinkText>1</LinkText></URL> , <URL><Link>../tutorial/chap2.html</Link><LinkText>2</LinkText></URL> , <URL><Link>../tutorial/chap3.html</Link><LinkText>3</LinkText></URL> , <URL><Link>../tutorial/chap4.html</Link><LinkText>4</LinkText></URL> , <URL><Link>../tutorial/chap5.html</Link><LinkText>5</LinkText></URL> , <URL><Link>../tutorial/chap10.html</Link><LinkText>6</LinkText></URL> , <URL><Link>../www/SideLinks/About/aboutMetrics.html</Link><LinkText>7</LinkText></URL> , <URL><Link>../www/SideLinks/About/aboutPersistent.html</Link><LinkText>8</LinkText></URL> , <URL><Link>../www/SideLinks/About/aboutCoveringSpaces.html</Link><LinkText>9</LinkText></URL> , <URL><Link>../www/SideLinks/About/aboutCoverinSpaces.html</Link><LinkText>10</LinkText></URL> , <URL><Link>../www/SideLinks/About/aboutCubical.html</Link><LinkText>11</LinkText></URL> , <URL><Link>../www/SideLinks/About/aboutRandomComplexes.html</Link><LinkText>12</LinkText></URL>
</Description> </ManSection>
<ManSection> <Func Name="SymmetricMatrixToFilteredGraph" Arg="A,m,s"/> <Func Name="SymmetricMatrixToFilteredGraph" Arg="A,m"/> <Description><P/> <P/>Inputs an <M>n \times n</M> symmetric matrix <M>A</M>, a positive integer <M>m</M> and a positive rational <M>s</M>. The function returns a filtered graph of filtration length <M>m</M>. The <M>t</M>-th term of the filtration is a graph with <M>n</M> vertices and an edge between the <M>i</M>-th and <M>j</M>-th vertices if the <M>(i,j)</M> entry of <M>A</M> is less than or equal to <M>t \times s/m</M>. <P/> If the optional input <M>s</M> is omitted then it is set equal to the largest entry in the matrix <M>A</M>. <P/><B>Examples:</B> <URL><Link>../tutorial/chap5.html</Link><LinkText>1</LinkText></URL> , <URL><Link>../tutorial/chap10.html</Link><LinkText>2</LinkText></URL> , <URL><Link>../www/SideLinks/About/aboutPersistent.html</Link><LinkText>3</LinkText></URL>
</Description> </ManSection>
<ManSection> <Func Name="SymmetricMatrixToGraph" Arg="A,t"/> <Description><P/> <P/> Inputs an <M>n\times n</M> symmetric matrix <M>A</M> over the rationals and a rational number <M>t \ge 0</M>, and returns the graph on the vertices <M>1,2, \ldots, n</M> with an edge between distinct vertices <M>i</M> and <M>j</M> precisely when the <M>(i,j)</M> entry of <M>A</M> is <M>\le t</M>. <P/><B>Examples:</B> <URL><Link>../tutorial/chap5.html</Link><LinkText>1</LinkText></URL> , <URL><Link>../www/SideLinks/About/aboutMetrics.html</Link><LinkText>2</LinkText></URL>
</Description> </ManSection> </Section> <Section><Heading> Metric Spaces</Heading>
<ManSection> <Func Name="CayleyMetric" Arg="g,h"/> <Description><P/> <P/> Inputs two permutations <M>g,h</M> and optionally the degree <M>N</M> of a symmetric group containing them. It returns the minimum number of transpositions needed to express <M>g*h^{-1}</M> as a product of transpositions. <P/><B>Examples:</B> <URL><Link>../www/SideLinks/About/aboutMetrics.html</Link><LinkText>1</LinkText></URL>
</Description> </ManSection>
<ManSection> <Var Name="EuclideanMetric"/> <Description><P/> <P/> Inputs two vectors <M>v,w \in \mathbb R^n</M> and returns a rational number approximating the Euclidean distance between them. <P/><B>Examples:</B>
</Description> </ManSection>
<ManSection> <Func Name="EuclideanSquaredMetric" Arg="g,h"/> <Description><P/> <P/> Inputs two vectors <M>v,w \in \mathbb R^n</M> and returns the square of the Euclidean distance between them. <P/><B>Examples:</B>
</Description> </ManSection>
<ManSection> <Func Name="HammingMetric" Arg="g,h"/> <Description><P/> <P/> Inputs two permutations <M>g,h</M> and optionally the degree <M>N</M> of a symmetric group containing them. It returns the minimum number of integers moved by the permutation <M>g*h^{-1}</M>. <P/><B>Examples:</B>
</Description> </ManSection>
<ManSection> <Func Name="KendallMetric" Arg="g,h"/> <Description><P/> <P/> Inputs two permutations <M>g,h</M> and optionally the degree <M>N</M> of a symmetric group containing them. It returns the minimum number of adjacent transpositions needed to express <M>g*h^{-1}</M> as a product of adjacent transpositions. An <E>adjacent</E> transposition is of the form <M>(i,i+1)</M>. <P/><B>Examples:</B>
</Description> </ManSection>
<ManSection> <Func Name="ManhattanMetric" Arg="g,h"/> <Description><P/> <P/> Inputs two vectors <M>v,w \in \mathbb R^n</M> and returns the Manhattan distance between them. <P/><B>Examples:</B> <URL><Link>../www/SideLinks/About/aboutMetrics.html</Link><LinkText>1</LinkText></URL>
</Description> </ManSection>
<ManSection> <Func Name="VectorsToSymmetricMatrix" Arg="V"/> <Func Name="VectorsToSymmetricMatrix" Arg="V,d"/> <Description><P/> <P/> Inputs a list <M>V =\{ v_1, \ldots, v_k\} \in \mathbb R^n</M> and returns the <M>k \times k</M> symmetric matrix of Euclidean distances <M>d(v_i, v_j)</M>. When these distances are irrational they are approximated by a rational number. <P/> As an optional second argument any rational valued function <M>d(x,y)</M> can be entered. <P/><B>Examples:</B> <URL><Link>../tutorial/chap5.html</Link><LinkText>1</LinkText></URL> , <URL><Link>../tutorial/chap10.html</Link><LinkText>2</LinkText></URL> , <URL><Link>../www/SideLinks/About/aboutMetrics.html</Link><LinkText>3</LinkText></URL>
</Description> </ManSection> </Section> <Section><Heading> Cellular Complexes <M>\longrightarrow</M> Cellular Complexes</Heading>
<ManSection> <Func Name="BoundaryMap" Arg="K"/> <Description><P/> <P/> Inputs a pure regular CW-complex <M>K</M> and returns the regular CW-inclusion map <M>\iota \colon \partial K \hookrightarrow K</M> from the boundary <M>\partial K</M> into the complex <M>K</M>. <P/><B>Examples:</B> <URL><Link>../tutorial/chap2.html</Link><LinkText>1</LinkText></URL> , <URL><Link>../tutorial/chap10.html</Link><LinkText>2</LinkText></URL> , <URL><Link>../www/SideLinks/About/aboutTopology.html</Link><LinkText>3</LinkText></URL>
</Description> </ManSection>
<ManSection> <Func Name="CliqueComplex" Arg="G,n"/> <Func Name="CliqueComplex" Arg="F,n"/> <Func Name="CliqueComplex" Arg="K,n"/> <Description><P/> <P/> Inputs a graph <M>G</M> and integer <M>n \ge 1</M>. It returns the <M>n</M>-skeleton of a simplicial complex <M>K</M> with one <M>k</M>-simplex for each complete subgraph of <M>G</M> on <M>k+1</M> vertices. <P/> Inputs a fitered graph <M>F</M> and integer <M>n \ge 1</M>. It returns the <M>n</M>-skeleton of a filtered simplicial complex <M>K</M> whose <M>t</M>-term has one <M>k</M>-simplex for each complete subgraph of the <M>t</M>-th term of <M>G</M> on <M>k+1</M> vertices. <P/> Inputs a simplicial complex of dimension <M>d=1</M> or <M>d=2</M>. If <M>d=1</M> then the clique complex of a graph returned. If <M>d=2</M> then the clique complex of a <M>2</M>-complex is returned. <P/><B>Examples:</B> <URL><Link>../tutorial/chap5.html</Link><LinkText>1</LinkText></URL>
</Description> </ManSection>
<ManSection> <Func Name="ConcentricFiltration" Arg="K,n"/> <Description><P/> <P/> Inputs a pure cubical complex <M>K</M> and integer <M>n \ge 1</M>, and returns a filtered pure cubical complex of filtration length <M>n</M>. The <M>t</M>-th term of the filtration is the intersection of <M>K</M> with the ball of radius <M>r_t</M> centred on the centre of gravity of <M>K</M>, where <M>0=r_1 \le r_2 \le r_3 \le \cdots \le r_n</M> are equally spaced rational numbers. The complex <M>K</M> is contained in the ball of radius <M>r_n</M>. (At present, this is implemented only for <M>2</M>- and <M>3</M>-dimensional complexes.) <P/><B>Examples:</B>
</Description> </ManSection>
<ManSection> <Func Name="DirectProduct" Arg="M,N"/> <Func Name="DirectProduct" Arg="M,N"/> <Description><P/> <P/> Inputs two or more regular CW-complexes or two or more pure cubical complexes and returns their direct product. <P/><B>Examples:</B> <URL><Link>../tutorial/chap1.html</Link><LinkText>1</LinkText></URL> , <URL><Link>../tutorial/chap3.html</Link><LinkText>2</LinkText></URL> , <URL><Link>../tutorial/chap10.html</Link><LinkText>3</LinkText></URL> , <URL><Link>../www/SideLinks/About/aboutCoveringSpaces.html</Link><LinkText>4</LinkText></URL> , <URL><Link>../www/SideLinks/About/aboutCoverinSpaces.html</Link><LinkText>5</LinkText></URL> , <URL><Link>../www/SideLinks/About/aboutCubical.html</Link><LinkText>6</LinkText></URL> , <URL><Link>../www/SideLinks/About/aboutExtensions.html</Link><LinkText>7</LinkText></URL>
</Description> </ManSection>
<ManSection> <Func Name="FiltrationTerm" Arg="K,t"/> <Func Name="FiltrationTerm" Arg="K,t"/> <Description> <P/> <P/> Inputs a filtered regular CW-complex or a filtered pure cubical complex <M>K</M> together with an integer <M>t \ge 1</M>. The <M>t</M>-th term of the filtration is returned. <P/><B>Examples:</B> <URL><Link>../tutorial/chap5.html</Link><LinkText>1</LinkText></URL>
</Description> </ManSection>
<ManSection> <Func Name="Graph" Arg="K"/> <Func Name="Graph" Arg="K"/> <Description><P/> <P/> Inputs a regular CW-complex or a simplicial complex <M>K</M> and returns its <M>1</M>-skeleton as a graph. <P/><B>Examples:</B> <URL><Link>../tutorial/chap1.html</Link><LinkText>1</LinkText></URL> , <URL><Link>../tutorial/chap2.html</Link><LinkText>2</LinkText></URL> , <URL><Link>../tutorial/chap5.html</Link><LinkText>3</LinkText></URL> , <URL><Link>../tutorial/chap7.html</Link><LinkText>4</LinkText></URL> , <URL><Link>../tutorial/chap10.html</Link><LinkText>5</LinkText></URL> , <URL><Link>../tutorial/chap11.html</Link><LinkText>6</LinkText></URL> , <URL><Link>../tutorial/chap14.html</Link><LinkText>7</LinkText></URL> , <URL><Link>../www/SideLinks/About/aboutMetrics.html</Link><LinkText>8</LinkText></URL> , <URL><Link>../www/SideLinks/About/aboutPersistent.html</Link><LinkText>9</LinkText></URL> , <URL><Link>../www/SideLinks/About/aboutRandomComplexes.html</Link><LinkText>10</LinkText></URL> , <URL><Link>../www/SideLinks/About/aboutSpaceGroup.html</Link><LinkText>11</LinkText></URL> , <URL><Link>../www/SideLinks/About/aboutGraphsOfGroups.html</Link><LinkText>12</LinkText></URL> , <URL><Link>../www/SideLinks/About/aboutIntro.html</Link><LinkText>13</LinkText></URL> , <URL><Link>../www/SideLinks/About/aboutTopology.html</Link><LinkText>14</LinkText></URL> , <URL><Link>../www/SideLinks/About/aboutTwistedCoefficients.html</Link><LinkText>15</LinkText></URL>
</Description> </ManSection>
<ManSection> <Func Name="HomotopyGraph" Arg="Y"/> <Description><P/> <P/> Inputs a regular CW-complex <M>Y</M> and returns a subgraph <M>M \subset Y^1</M> of the <M>1</M>-skeleton for which the induced homology homomorphisms <M>H_1(M,\mathbb Z) \rightarrow H_1(Y,\mathbb Z)</M> and <M>H_1(Y^1,\mathbb Z) \rightarrow H_1(Y,\mathbb Z)</M> have identical images. The construction tries to include as few edges in <M>M</M> as possible, though a minimum is not guaranteed. <P/><B>Examples:</B> <URL><Link>../tutorial/chap5.html</Link><LinkText>1</LinkText></URL>
</Description> </ManSection>
<ManSection> <Func Name="Nerve" Arg="M"/> <Func Name="Nerve" Arg="M"/> <Func Name="Nerve" Arg="M,n"/> <Func Name="Nerve" Arg="M,n"/> <Description><P/> <P/>Inputs a pure cubical complex or pure permutahedral complex <M>M</M> and returns the simplicial complex <M>K</M> obtained by taking the nerve of an open cover of <M>|M|</M>, the open sets in the cover being sufficiently small neighbourhoods of the top-dimensional cells of <M>|M|</M>. The spaces <M>|M|</M> and <M>|K|</M> are homotopy equivalent by the Nerve Theorem. If an integer <M>n \ge 0</M> is supplied as the second argument then only the n-skeleton of <M>K</M> is returned. <P/><B>Examples:</B> <URL><Link>../tutorial/chap1.html</Link><LinkText>1</LinkText></URL> , <URL><Link>../tutorial/chap2.html</Link><LinkText>2</LinkText></URL> , <URL><Link>../tutorial/chap10.html</Link><LinkText>3</LinkText></URL> , <URL><Link>../tutorial/chap12.html</Link><LinkText>4</LinkText></URL> , <URL><Link>../www/SideLinks/About/aboutMetrics.html</Link><LinkText>5</LinkText></URL> , <URL><Link>../www/SideLinks/About/aboutPersistent.html</Link><LinkText>6</LinkText></URL> , <URL><Link>../www/SideLinks/About/aboutRandomComplexes.html</Link><LinkText>7</LinkText></URL> , <URL><Link>../www/SideLinks/About/aboutSimplicialGroups.html</Link><LinkText>8</LinkText></URL> , <URL><Link>../www/SideLinks/About/aboutIntro.html</Link><LinkText>9</LinkText></URL>
</Description> </ManSection>
<ManSection> <Func Name="RegularCWComplex" Arg="K"/> <Func Name="RegularCWComplex" Arg="K"/> <Func Name="RegularCWComplex" Arg="K"/> <Func Name="RegularCWComplex" Arg="K"/> <Func Name="RegularCWComplex" Arg="L"/> <Func Name="RegularCWComplex" Arg="L,M"/> <Description><P/> <P/>Inputs a simplicial, pure cubical, cubical or pure permutahedral complex <M>K</M> and returns the corresponding regular CW-complex. Inputs a list <M>L=Y!.boundaries</M> of boundary incidences of a regular CW-complex <M>Y</M> and returns <M>Y</M>. Inputs a list <M>L=Y!.boundaries</M> of boundary incidences of a regular CW-complex <M>Y</M> together with a list <M>M=Y!.orientation</M> of incidence numbers and returns a regular CW-complex <M>Y</M>. The availability of precomputed incidence numbers saves recalculating them. <P/><B>Examples:</B> <URL><Link>../tutorial/chap1.html</Link><LinkText>1</LinkText></URL> , <URL><Link>../tutorial/chap2.html</Link><LinkText>2</LinkText></URL> , <URL><Link>../tutorial/chap3.html</Link><LinkText>3</LinkText></URL> , <URL><Link>../tutorial/chap4.html</Link><LinkText>4</LinkText></URL> , <URL><Link>../tutorial/chap5.html</Link><LinkText>5</LinkText></URL> , <URL><Link>../tutorial/chap10.html</Link><LinkText>6</LinkText></URL> , <URL><Link>../tutorial/chap14.html</Link><LinkText>7</LinkText></URL> , <URL><Link>../www/SideLinks/About/aboutMetrics.html</Link><LinkText>8</LinkText></URL> , <URL><Link>../www/SideLinks/About/aboutPeripheral.html</Link><LinkText>9</LinkText></URL> , <URL><Link>../www/SideLinks/About/aboutCoveringSpaces.html</Link><LinkText>10</LinkText></URL> , <URL><Link>../www/SideLinks/About/aboutCoverinSpaces.html</Link><LinkText>11</LinkText></URL> , <URL><Link>../www/SideLinks/About/aboutRandomComplexes.html</Link><LinkText>12</LinkText></URL> , <URL><Link>../www/SideLinks/About/aboutKnots.html</Link><LinkText>13</LinkText></URL>
</Description> </ManSection>
<ManSection> <Func Name="RegularCWMap" Arg="M,A"/> <Description><P/> <P/> Inputs a pure cubical complex <M>M</M> and a subcomplex <M>A</M> and returns the inclusion map <M>A \rightarrow M</M> as a map of regular CW complexes. <P/><B>Examples:</B> <URL><Link>../tutorial/chap4.html</Link><LinkText>1</LinkText></URL> , <URL><Link>../www/SideLinks/About/aboutCoveringSpaces.html</Link><LinkText>2</LinkText></URL> , <URL><Link>../www/SideLinks/About/aboutCoverinSpaces.html</Link><LinkText>3</LinkText></URL>
</Description> </ManSection>
<ManSection> <Func Name="ThickeningFiltration" Arg="K,n"/> <Func Name="ThickeningFiltration" Arg="K,n,s"/> <Description><P/> <P/> Inputs a pure cubical complex <M>K</M> and integer <M>n \ge 1</M>, and returns a filtered pure cubical complex of filtration length <M>n</M>. The <M>t</M>-th term of the filtration is the <M>t</M>-fold thickening of <M>K</M>. If an integer <M>s \ge 1</M> is entered as the optional third | | |