Class: NetworkX::MultiGraph

Inherits:
Graph
  • Object
show all
Defined in:
lib/networkx/multigraph.rb

Overview

Describes the class for making MultiGraphs

Instance Attribute Summary collapse

Instance Method Summary collapse

Methods inherited from Graph

#add_edges, #add_node, #add_nodes, #add_weighted_edge, #add_weighted_edges, #clear, #directed?, #get_edge_data, #get_node_data, #initialize, #multigraph?, #neighbours, #node?, #number_of_nodes, #remove_edges, #remove_node, #remove_nodes

Constructor Details

This class inherits a constructor from NetworkX::Graph

Instance Attribute Details

#adj ⇒ Hash{ Object => Hash{ Object => Hash{ Integer => Hash{ Object => Object } } } } (readonly)

Stores the edges and their attributes in an adjencency list form

Returns:

  • (Hash{ Object => Hash{ Object => Hash{ Integer => Hash{ Object => Object } } } }) —

    the current value of adj



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# File 'lib/networkx/multigraph.rb', line 8

def adj
  @adj
end

#graph ⇒ Hash{ Object => Object } (readonly)

Stores the attributes of the gra

Returns:

  • (Hash{ Object => Object }) —

    the current value of graph



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# File 'lib/networkx/multigraph.rb', line 8

def graph
  @graph
end

#nodes ⇒ Hash{ Object => Hash{ Object => Object } } (readonly)

Stores the nodes and their attributes

Returns:

  • (Hash{ Object => Hash{ Object => Object } }) —

    the current value of nodes



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# File 'lib/networkx/multigraph.rb', line 8

def nodes
  @nodes
end

Instance Method Details

#add_edge(node_1, node_2, **edge_attrs) ⇒ Object

Adds the respective edge

Examples:

Add an edge with attribute name

graph.add_edge(node1, node2, name: "Edge1")

Add an edge with no attribute

graph.add_edge("Bangalore", "Chennai")

Parameters:

  • node_1 (Object) —

    the first node of the edge

  • node_2 (Object) —

    the second node of the edge

  • edge_attrs (Hash{ Object => Object }) —

    the hash of the edge attributes



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# File 'lib/networkx/multigraph.rb', line 31

def add_edge(node_1, node_2, **edge_attrs)
  add_node(node_1)
  add_node(node_2)
  key = new_edge_key(node_1, node_2)
  all_edge_attrs = @adj[node_1][node_2] || {}
  all_edge_attrs[key] = edge_attrs
  @adj[node_1][node_2] = all_edge_attrs
  @adj[node_2][node_1] = all_edge_attrs
end

#edge?(node_1, node_2, key = nil) ⇒ Boolean

Checks if the the edge consisting of two nodes is present in the graph

Examples:

graph.edge?(node_1, node_2)

Parameters:

  • node_1 (Object) —

    the first node of the edge to be checked

  • node_2 (Object) —

    the second node of the edge to be checked

  • key (Integer) (defaults to: nil) —

    the key of the given edge

Returns:

  • (Boolean) 


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# File 'lib/networkx/multigraph.rb', line 97

def edge?(node_1, node_2, key=nil)
  super(node_1, node_2) if key.nil?
  node?(node_1) && @adj[node_1].key?(node_2) && @adj[node_1][node_2].key?(key)
end

#edge_subgraph(edges) ⇒ Object

Returns subgraph conisting of given edges

Examples:

graph.edge_subgraph([%w[Nagpur Wardha], %w[Nagpur Mumbai]])

Parameters:

  • edges (Array<Object, Object>) —

    the edges to be included in the subraph



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# File 'lib/networkx/multigraph.rb', line 153

def edge_subgraph(edges)
  case edges
  when Array, Set
    sub_graph = NetworkX::MultiGraph.new(@graph)
    edges.each do |u, v|
      raise KeyError, "Edge between #{u} and #{v} does not exist in the graph!" unless @nodes.key?(u)\
                                                                                && @adj[u].key?(v)
      sub_graph.add_node(u, @nodes[u])
      sub_graph.add_node(v, @nodes[v])
      @adj[u][v].each { |_, keyval| sub_graph.add_edge(u, v, keyval) }
    end
    return sub_graph
  else
    raise ArgumentError, 'Expected Argument to be Array or Set of edges, '\
    "received #{edges.class.name} instead."
  end
end

#new_edge_key(node_1, node_2) ⇒ Object

Returns a new key

Parameters:

  • node_1 (Object) —

    the first node of a given edge

  • node_2 (Object) —

    the second node of a given edge



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# File 'lib/networkx/multigraph.rb', line 13

def new_edge_key(node_1, node_2)
  return 0 if @adj[node_1][node_2].nil?
  key = @adj[node_1][node_2].length
  key += 1 while @adj[node_1][node_2].key?(key)
  key
end

#number_of_edges ⇒ Object

Returns number of edges

Examples:

graph.number_of_edges


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# File 'lib/networkx/multigraph.rb', line 85

def number_of_edges
  @adj.values.flat_map(&:values).map(&:length).inject(:+) / 2
end

#remove_edge(node_1, node_2, key = nil) ⇒ Object

Removes edge from the graph

Examples:

graph.remove_edge('Noida', 'Bangalore')

Parameters:

  • node_1 (Object) —

    the first node of the edge

  • node_2 (Object) —

    the second node of the edge

Raises:

  • (KeyError) 


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# File 'lib/networkx/multigraph.rb', line 50

def remove_edge(node_1, node_2, key=nil)
  if key.nil?
    super(node_1, node_2)
    return
  end
  raise KeyError, "#{node_1} is not a valid node." unless @nodes.key?(node_1)
  raise KeyError, "#{node_2} is not a valid node" unless @nodes.key?(node_2)
  raise KeyError, 'The given edge is not a valid one.' unless @adj[node_1].key?(node_2)
  raise KeyError, 'The given edge is not a valid one.' unless @adj[node_1][node_2].key?(key)
  @adj[node_1][node_2].delete(key)
  @adj[node_2][node_1].delete(key)
end

#size(is_weighted = false) ⇒ Object

Returns the size of the graph

Examples:

graph.size(true)

Parameters:

  • is_weighted (Bool) (defaults to: false) —

    if true, method returns sum of weights of all edges else returns number of edges



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# File 'lib/networkx/multigraph.rb', line 70

def size(is_weighted=false)
  if is_weighted
    graph_size = 0
    @adj.each do |_, hash_val|
      hash_val.each { |_, v| v.each { |_, attrs| graph_size += attrs[:weight] if attrs.key?(:weight) } }
    end
    return graph_size / 2
  end
  number_of_edges
end

#subgraph(nodes) ⇒ Object

Returns subgraph consisting of given array of nodes

Examples:

graph.subgraph(%w[Mumbai Nagpur])

Parameters:

  • nodes (Array<Object>) —

    the nodes to be included in the subgraph



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# File 'lib/networkx/multigraph.rb', line 127

def subgraph(nodes)
  case nodes
  when Array, Set
    sub_graph = NetworkX::MultiGraph.new(@graph)
    nodes.each do |u, _|
      raise KeyError, "#{u} does not exist in the current graph!" unless @nodes.key?(u)
      sub_graph.add_node(u, @nodes[u])
      @adj[u].each do |v, edge_val|
        edge_val.each { |_, keyval| sub_graph.add_edge(u, v, keyval) if @adj[u].key?(v) && nodes.include?(v) }
      end
      return sub_graph
    end
  else
    raise ArgumentError, 'Expected Argument to be Array or Set of nodes, '\
                         "received #{nodes.class.name} instead."
  end
end

#to_undirected ⇒ Object

Returns the undirected version of the graph

Examples:

graph.to_undirected


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# File 'lib/networkx/multigraph.rb', line 106

def to_undirected
  graph = NetworkX::Graph.new(@graph)
  @nodes.each { |node, node_attr| graph.add_node(node, node_attr) }
  @adj.each do |node_1, node_1_edges|
    node_1_edges.each do |node_2, node_1_node_2|
      edge_attrs = {}
      node_1_node_2.each { |_key, attrs| edge_attrs.merge!(attrs) }
      graph.add_edge(node_1, node_2, edge_attrs)
    end
  end
  graph
end