# R igraph manual pages

Use this if you are using igraph from R

## Is a degree sequence graphical?

### Description

Determine whether the given vertex degrees (in- and out-degrees for directed graphs) can be realized in a simple graph, i.e. a graph without multiple or loop edges.

### Usage

is_graphical(out.deg, in.deg = NULL)


### Arguments

 out.deg Integer vector, the degree sequence for undirected graphs, or the out-degree sequence for directed graphs. in.deg NULL or an integer vector. For undirected graphs, it should be NULL. For directed graphs it specifies the in-degrees.

### Value

A logical scalar.

### Author(s)

Tamas Nepusz ntamas@gmail.com

### References

Hakimi SL: On the realizability of a set of integers as degrees of the vertices of a simple graph. J SIAM Appl Math 10:496-506, 1962.

PL Erdos, I Miklos and Z Toroczkai: A simple Havel-Hakimi type algorithm to realize graphical degree sequences of directed graphs. The Electronic Journal of Combinatorics 17(1):R66, 2010.

Other graphical degree sequences: is_degseq()
g <- sample_gnp(100, 2/100)