R: Load a graph from the graph database for testing graph...

graph_from_graphdb {igraph} | R Documentation

## Load a graph from the graph database for testing graph isomorphism.

### Description

This function downloads a graph from a database created for the evaluation of graph isomorphism testing algothitms.

### Usage

    graph_from_graphdb(url = NULL, prefix = "iso", type = "r001",
      nodes = NULL, pair = "A", which = 0,
      base = "http://cneurocvs.rmki.kfki.hu/graphdb/gzip", compressed = TRUE,
      directed = TRUE)

### Arguments

`url` | If not `NULL` it is a complete URL with the file to import.
`prefix` | Gives the prefix. See details below. Possible values: `iso`, `i2`, `si4`, `si6`, `mcs10`, `mcs30`, `mcs50`, `mcs70`, `mcs90`.
`type` | Gives the graph type identifier. See details below. Possible values: `r001`, `r005`, `r01`, `r02`, `m2D`, `m2Dr2`, `m2Dr4`, `m2Dr6` `m3D`, `m3Dr2`, `m3Dr4`, `m3Dr6`, `m4D`, `m4Dr2`, `m4Dr4`, `m4Dr6`, `b03`, `b03m`, `b06`, `b06m`, `b09`, `b09m`.
`nodes` | The number of vertices in the graph.
`pair` | Specifies which graph of the pair to read. Possible values: `A` and `B`.
`which` | Gives the number of the graph to read. For every graph type there are a number of actual graphs in the database. This argument specifies which one to read.
`base` | The base address of the database. See details below.
`compressed` | Logical constant, if TRUE than the file is expected to be compressed by gzip. If `url` is `NULL` then a ‘`.gz`’ suffix is added to the filename.
`directed` | Logical constant, whether to create a directed graph.

### Details

`graph_from_graphdb` reads a graph from the graph database from an FTP or HTTP server or from a local copy. It has two modes of operation:

If the `url` argument is specified then it should the complete path to a local or remote graph database file. In this case we simply call `read_graph` with the proper arguments to read the file.

If `url` is `NULL`, and this is the default, then the filename is assembled from the `base`, `prefix`, `type`, `nodes`, `pair` and `which` arguments.

Unfortunately the original graph database homepage is now defunct, but see its old version at http://web.archive.org/web/20090215182331/http://amalfi.dis.unina.it/graph/db/doc/graphdbat.html for the actual format of a graph database file and other information.

### Value

A new graph object.

### Examples

    g <- graph_from_graphdb(prefix="iso", type="r001", nodes=20, pair="A",
      which=10, compressed=TRUE)
    g2 <- graph_from_graphdb(prefix="iso", type="r001", nodes=20, pair="B",
      which=10, compressed=TRUE)
    graph.isomorphic.vf2(g, g2)	% should be TRUE
    g3 <- graph_from_graphdb(url=paste(sep="/",
                                  "http://cneurocvs.rmki.kfki.hu",
                                  "graphdb/gzip/iso/bvg/b06m",
                                  "iso_b06m_m200.A09.gz"))

### Author(s)

Gabor Csardi csardi.gabor@gmail.com

### References

M. De Santo, P. Foggia, C. Sansone, M. Vento: A large database of graphs and its use for benchmarking graph isomorphism algorithms, Pattern Recognition Letters, Volume 24, Issue 8 (May 2003)

### See Also

`read_graph`, `graph.isomorphic.vf2`

[Package igraph version 1.2.2 Index]