3.1. igraph_read_graph_graphml — Reads a graph from a GraphML file.

3.1. `igraph_read_graph_graphml` — Reads a graph from a GraphML file.

int igraph_read_graph_graphml(igraph_t *graph, FILE *instream,
			      int index);

GraphML is an XML-based file format for representing various types of graphs. Currently only the most basic import functionality is implemented in igraph: it can read GraphML files without nested graphs and hyperedges. Attributes of the graph are loaded only if an attribute interface is attached, ie. if you use igraph from R or Python.

Arguments:

`graph`:	Pointer to an uninitialized graph object.
`instream`:	A stream, it should be readable.
`index`:	If the GraphML file contains more than one graph, the one specified by this index will be loaded. Indices start from zero, so supply zero here if your GraphML file contains only a single graph.

Returns:

Error code: IGRAPH_PARSEERROR: if there is a problem reading the file, or the file is syntactically incorrect. IGRAPH_UNIMPLEMENTED: the GraphML functionality was disabled at compile-time