`class CohesiveBlocks(VertexCover):`

The cohesive block structure of a graph.

Instances of this type are created by `Graph.cohesive_blocks()`

. See the documentation of `Graph.cohesive_blocks()`

for an explanation of what cohesive blocks are.

This class provides a few more methods that make handling of cohesive block structures easier.

Method | `__init__` |
Constructs a new cohesive block structure for the given graph. |

Method | `__plot__` |
Plots the cohesive block structure to the given Cairo context in the given bounding box. |

Method | `cohesion` |
Returns the cohesion of the group with the given index. |

Method | `cohesions` |
Returns the list of cohesion values for each group. |

Method | `hierarchy` |
Returns a new graph that describes the hierarchical relationships between the groups. |

Method | `max` |
Finds the maximum cohesion score among all the groups that contain the given vertex. |

Method | `max` |
For each vertex in the graph, returns the maximum cohesion score among all the groups that contain the vertex. |

Method | `parent` |
Returns the parent group index of the group with the given index or None if the given group is the root. |

Method | `parents` |
Returns the list of parent group indices for each group or None if the given group is the root. |

Instance Variable | `_cohesion` |
Undocumented |

Instance Variable | `_parent` |
Undocumented |

Inherited from `VertexCover`

:

Method | `crossing` |
Returns a boolean vector where element i is True iff edge i lies between clusters, False otherwise. |

Method | `subgraph` |
Get the subgraph belonging to a given cluster. |

Method | `subgraphs` |
Gets all the subgraphs belonging to each of the clusters. |

Property | `graph` |
Returns the graph belonging to this object |

Method | `_formatted` |
Iterates over the clusters and formats them into a string to be presented in the summary. |

Instance Variable | `_graph` |
Undocumented |

Inherited from `Cover`

(via `VertexCover`

):

Method | `__getitem__` |
Returns the cluster with the given index. |

Method | `__iter__` |
Iterates over the clusters in this cover. |

Method | `__len__` |
Returns the number of clusters in this cover. |

Method | `__str__` |
Returns a string representation of the cover. |

Method | `size` |
Returns the size of a given cluster. |

Method | `size` |
Returns the histogram of cluster sizes. |

Method | `sizes` |
Returns the size of given clusters. |

Method | `summary` |
Returns the summary of the cover. |

Property | `membership` |
Returns the membership vector of this cover. |

Property | `n` |
Returns the number of elements in the set covered by this cover. |

Instance Variable | `_clusters` |
Undocumented |

Instance Variable | `_n` |
Undocumented |

`igraph.clustering.VertexCover.__init__`

Constructs a new cohesive block structure for the given graph.

If any of *blocks*, *cohesion* or *parent* is `None`, all the arguments will be ignored and `Graph.cohesive_blocks()`

will be called to calculate the cohesive blocks. Otherwise, these three variables should describe the *result* of a cohesive block structure calculation. Chances are that you never have to construct `CohesiveBlocks`

instances directly, just use `Graph.cohesive_blocks()`

.

Parameters | |

graph | the graph itself |

blocks | a list containing the blocks; each block is described as a list containing vertex IDs. |

cohesion | the cohesion of each block. The length of this list must be equal to the length of blocks. |

parent | the parent block of each block. Negative values or None mean that there is no parent block for that block. There should be only one parent block, which covers the entire graph. |

See Also | |

Graph.cohesive_blocks() |

`igraph.clustering.VertexCover.__plot__`

Plots the cohesive block structure to the given Cairo context in the given bounding box.

Since a `CohesiveBlocks`

instance is also a `VertexCover`

, keyword arguments accepted by `VertexCover.__plot__()`

are also accepted here. The only difference is that the vertices are colored according to their maximal cohesions by default, and groups are marked by colored blobs except the last group which encapsulates the whole graph.

See the documentation of `VertexCover.__plot__()`

for more details.

Returns a new graph that describes the hierarchical relationships between the groups.

The new graph will be a directed tree; an edge will point from vertex *i* to vertex *j* if group *i* is a superset of group *j*. In other words, the edges point downwards.

For each vertex in the graph, returns the maximum cohesion score among all the groups that contain the vertex.

Returns the parent group index of the group with the given index or `None` if the given group is the root.