# 3.3.3.103. NXgraph_edge_set¶

**Status**:

base class, extends NXobject

**Description**:

A set of (eventually directed) edges which connect nodes/vertices of a graph.

**Symbols**:

The symbols used in the schema to specify e.g. dimensions of arrays.

n_edges: The number of edges.

**Groups cited**:none

**Structure**:

number_of_edges: (optional) NX_POSINT {units=NX_UNITLESS}Total number of edges, counting eventual bidirectional edges only once.

identifier_offset: (optional) NX_INT {units=NX_UNITLESS}## Integer which specifies the first index to be used for distinguishing ...

Integer which specifies the first index to be used for distinguishing edges. Identifiers are defined either implicitly or explicitly. For implicit indexing the identifiers are defined on the interval [identifier_offset, identifier_offset+c-1]. For explicit indexing the identifier array has to be defined.

The identifier_offset field can for example be used to communicate if the identifiers are expected to start from 1 (referred to as Fortran-/Matlab-) or from 0 (referred to as C-, Python-style index notation) respectively.

identifier: (optional) NX_INT (Rank: 1, Dimensions: [n_edges]) {units=NX_UNITLESS}Integer used to distinguish edges for explicit indexing.

directionality: (optional) NX_INT (Rank: 1, Dimensions: [n_edges]) {units=NX_UNITLESS}## Specifier whether each edge is non-directional, one-directional, ...

Specifier whether each edge is non-directional, one-directional, or bidirectional. Use the smallest available binary representation which can store three different states:

0 / state 0x00 is non-directional

1 / state 0x01 is one-directional

2 / state 0x02 is bi-directional

node_pair: (optional) NX_INT (Rank: 2, Dimensions: [n_edges, 2]) {units=NX_UNITLESS}## Pairs of node/vertex identifier. Each pair represents the connection ...

Pairs of node/vertex identifier. Each pair represents the connection between two nodes.

In the case that the edge is non- or bi-directional node identifier should be stored in ascending order is preferred.

In the case of one-directional, for each pair the identifier of the source node is the first entry in the pair. The identifier of the target is the second entry in the pair, i.e. the pair encodes the information as if one traverses the edge from the source node walking to the target node.

is_a: (optional) NX_CHAR (Rank: 1, Dimensions: [c])## A human-readable qualifier which type or e.g. class instance the ...

A human-readable qualifier which type or e.g. class instance the edge is an instance of.

label: (optional) NX_CHAR (Rank: 1, Dimensions: [n_edges])A human-readable label/caption/tag for the edge.

## Hypertext Anchors¶

List of hypertext anchors for all groups, fields, attributes, and links defined in this class.