# R igraph manual pages

Use this if you are using igraph from R

### Description

The read_graph function is able to read graphs in various representations from a file, or from a http connection. Various formats are supported.

### Usage

read_graph(
file,
format = c("edgelist", "pajek", "ncol", "lgl", "graphml", "dimacs", "graphdb", "gml",
"dl"),
...
)


### Arguments

 file The connection to read from. This can be a local file, or a http or ftp connection. It can also be a character string with the file name or URI. format Character constant giving the file format. Right now edgelist, pajek, ncol, lgl, graphml, dimacs, graphdb, gml and dl are supported, the default is edgelist. As of igraph 0.4 this argument is case insensitive. ... Additional arguments, see below.

### Details

The read_graph function may have additional arguments depending on the file format (the format argument). See the details separately for each file format, below.

A graph object.

### Edge list format

This format is a simple text file with numeric vertex ids defining the edges. There is no need to have newline characters between the edges, a simple space will also do.

n

The number of vertices in the graph. If it is smaller than or equal to the largest integer in the file, then it is ignored; so it is safe to set it to zero (the default).

directed

Logical scalar, whether to create a directed graph. The default value is TRUE.

### Author(s)

Gabor Csardi csardi.gabor@gmail.com

write_graph