# Core functions

Graphs.jl includes the following core functions.

## Full docs

Graphs.add_vertices!Method
add_vertices!(g, n)

Add n new vertices to the graph g. Return the number of vertices that were added successfully.

Examples

julia> using Graphs

julia> g = SimpleGraph()
{0, 0} undirected simple Int64 graph

2
source
Graphs.all_neighborsFunction
all_neighbors(g, v)

Return a list of all inbound and outbound neighbors of v in g. For undirected graphs, this is equivalent to both outneighbors and inneighbors.

Implementation Notes

Returns a reference to the current graph's internal structures, not a copy. Do not modify result. If the graph is modified, the behavior is undefined: the array behind this reference may be modified too, but this is not guaranteed.

Examples

julia> using Graphs

julia> g = DiGraph(3);

julia> all_neighbors(g, 1)
1-element Array{Int64,1}:
3

julia> all_neighbors(g, 2)
1-element Array{Int64,1}:
3

julia> all_neighbors(g, 3)
2-element Array{Int64,1}:
1
2
source
Graphs.common_neighborsMethod
common_neighbors(g, u, v)

Return the neighbors common to vertices u and v in g.

Implementation Notes

Returns a reference to the current graph's internal structures, not a copy. Do not modify result. If the graph is modified, the behavior is undefined: the array behind this reference may be modified too, but this is not guaranteed.

Examples

julia> using Graphs

julia> g = SimpleGraph(4);

julia> common_neighbors(g, 1, 3)
2-element Array{Int64,1}:
2
4

julia> common_neighbors(g, 1, 4)
1-element Array{Int64,1}:
3
source
Graphs.degreeFunction
degree(g[, v])

Return a vector corresponding to the number of edges which start or end at each vertex in graph g. If v is specified, only return degrees for vertices in v. For directed graphs, this value equals the incoming plus outgoing edges. For undirected graphs, it equals the connected edges.

Examples

julia> using Graphs

julia> g = DiGraph(3);

julia> degree(g)
3-element Array{Int64,1}:
1
1
2
source
Graphs.densityFunction
density(g)

Return the density of g. Density is defined as the ratio of the number of actual edges to the number of possible edges ($|V|×(|V|-1)$ for directed graphs and $\frac{|V|×(|V|-1)}{2}$ for undirected graphs).

source
Graphs.has_self_loopsMethod
has_self_loops(g)

Return true if g has any self loops.

Examples

julia> using Graphs

julia> g = SimpleGraph(2);

julia> has_self_loops(g)
false

julia> has_self_loops(g)
true
source
Graphs.indegreeMethod
indegree(g[, v])

Return a vector corresponding to the number of edges which end at each vertex in graph g. If v is specified, only return degrees for vertices in v.

Examples

julia> using Graphs

julia> g = DiGraph(3);

julia> indegree(g)
3-element Array{Int64,1}:
1
0
1
source
Graphs.is_orderedMethod
is_ordered(e)

Return true if the source vertex of edge e is less than or equal to the destination vertex.

Examples

julia> using Graphs

julia> g = DiGraph(2);

julia> is_ordered(first(edges(g)))
false
source
Graphs.neighborsMethod
neighbors(g, v)

Return a list of all neighbors reachable from vertex v in g. For directed graphs, the default is equivalent to outneighbors; use all_neighbors to list inbound and outbound neighbors.

Implementation Notes

Returns a reference to the current graph's internal structures, not a copy. Do not modify result. If the graph is modified, the behavior is undefined: the array behind this reference may be modified too, but this is not guaranteed.

Examples

julia> using Graphs

julia> g = DiGraph(3);

julia> neighbors(g, 1)
0-element Array{Int64,1}

julia> neighbors(g, 2)
1-element Array{Int64,1}:
3

julia> neighbors(g, 3)
1-element Array{Int64,1}:
1
source
Graphs.noallocextremeMethod
noallocextreme(f, comparison, initial, g)

Compute the extreme value of [f(g,i) for i=i:nv(g)] without gathering them all

source
Graphs.num_self_loopsMethod
num_self_loops(g)

Return the number of self loops in g.

Examples

julia> using Graphs

julia> g = SimpleGraph(2);

julia> num_self_loops(g)
0

julia> num_self_loops(g)
1
source
Graphs.outdegreeMethod
outdegree(g[, v])

Return a vector corresponding to the number of edges which start at each vertex in graph g. If v is specified, only return degrees for vertices in v.

Examples

julia> using Graphs

julia> g = DiGraph(3);

julia> outdegree(g)
3-element Array{Int64,1}:
0
1
1
source
Graphs.squashMethod
squash(g)

Return a copy of a graph with the smallest practical eltype that can accommodate all vertices.

May also return the original graph if the eltype does not change.

source