Reading foreign file formats
read_graph function is able to read graphs in various
representations from a file, or from a http connection. Currently some
simple formats are supported.
read_graph(file, format = c("edgelist", "pajek", "ncol", "lgl", "graphml", "dimacs", "graphdb", "gml", "dl"), ...)
The connection to read from. This can be a local file, or a
ftpconnection. It can also be a character string with the file name or URI.
Character constant giving the file format. Right now
graphdbare supported, the default is
edgelist. As of igraph 0.4 this argument is case insensitive.
Additional arguments, see below.
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.
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).
Logical scalar, whether to create a directed graph. The default value is