graph theory: degree sequence function

[sagetrac-mvngu]

The degree sequence of a graph is a basic property that is studied in an introductory course on graph theory. There should be examples explaining how to compute the degree sequence of a given graph.

Component: graph theory

Author: Minh Van Nguyen

Reviewer: Karl-Dieter Crisman, Nathann Cohen

Merged: sage-4.3.alpha1

Issue created by migration from https://trac.sagemath.org/ticket/7564

[sagetrac-mvngu]

comment:1

The patch trac_7564-degree-sequences.patch adds two examples to the method GenericGraph.degree(), showcasing how to obtain the degree sequence of a graph using that method.

[sagetrac-mvngu]

Author: Minh Van Nguyen

[kcrisman]

comment:2

I will ask for more, if it isn't too much trouble. Could there be a small wrapper to (the better one) called degree_sequence as well? I realize this is very low priority. If the graph theory tour ever gets back up, this would be ideal to put in it as well.

[sagetrac-mvngu]

comment:3

Replying to @kcrisman:

Could there be a small wrapper to (the better one) called degree_sequence as well?

As I mentioned in my email to sage-devel, I'm unable to find a function or method in the graph theory module that computes the degree sequence of a given graph. So there is no function or method for wrapping, unless you can point me to such a method/function. On the other hand, are you suggesting that there be a method in the class GenericGraph called degree_sequence() that does exactly as its name implies? If so, then that could be done.

If the graph theory tour ever gets back up, this would be ideal to put in it as well.

Nod.

[kcrisman]

comment:4

Replying to @sagetrac-mvngu:

Replying to @kcrisman:

Could there be a small wrapper to (the better one) called degree_sequence as well?

As I mentioned in my email to sage-devel, I'm unable to find a function or method in the graph theory module that computes the degree sequence of a given graph. So there is no function or method for wrapping, unless you can point me to such a method/function. On the other hand, are you suggesting that there be a method in the class GenericGraph called degree_sequence() that does exactly as its name implies? If so, then that could be done.

Yes, that is exactly what I meant - wrapping the examples you provide, as it were. I don't have time to do this, unfortunately, though it should be pretty easy.

[sagetrac-mvngu]

comment:5

The (new) patch trac_7564-degree-sequences.patch defines the method GenericGraph.degree_sequence() for computing the degree sequence of a graph.

[nathanncohen]

comment:6

Could it be possible to define in the same patch functions outdegree_sequence and indegree_sequence for DiGraphs ? :-)

[sagetrac-mvngu]

based on Sage 4.3.alpha0

[sagetrac-mvngu]

comment:7

Attachment: trac_7564-degree-sequences.patch.gz

Replying to @nathanncohen:

Could it be possible to define in the same patch functions outdegree_sequence and indegree_sequence for DiGraphs ? :-)

Y-E-S, yes! :-)

The patch trac_7564-degree-sequences.patch implements the following degree sequences:

1. degree_sequence() --- the degree sequence of a (di)graph. This is implemented in the class GenericGraph.
2. in_degree_sequence() --- the indegree sequence of a digraph. This is implemented in the class DiGraph.
3. out_degree_sequence() --- the outdegree sequence of a digraph, also implemented in the class DiGraph.

I use the method names in_degree_sequence() and out_degree_sequence() to be consistent with how the graph theory module names the indegree and outdegree methods.

[nathanncohen]

comment:8

Excellent ! Approved :-)

Thank you for contributing to the Graph Section !! :-)

[mwhansen]

Reviewer: Karl-Dieter Crisman, Nathann Cohen

[mwhansen]

Merged: sage-4.3.alpha1

[nathanncohen]

comment:10

A patch written, reviewed and merged in 11 hours ? O_O

God O_O