R: Is a degree sequence graphical?

is_graphical {igraph} | R Documentation

## Is a degree sequence graphical?

### Description

Determine whether the given vertex degrees (in- and out-degrees for directed graphs) can be reliazed 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 undireted 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.

### See Also

Other graphical degree sequences: `is_degseq()`

### Examples

    g <- sample_gnp(100, 2/100)
    is_degseq(degree(g))
    is_graphical(degree(g))

[Package igraph version 1.2.6 Index]