# dgl.node_type_subgraph¶

dgl.node_type_subgraph(graph, ntypes)[source]

Return the subgraph induced on given node types.

A node-type-induced subgraph contains all the nodes of the given subset of the node types of a graph and any edges whose endpoints are both in this subset. In addition to extracting the subgraph, DGL also copies the features of the extracted nodes and edges to the resulting graph. The copy is lazy and incurs data movement only when needed.

Parameters
• graph (DGLGraph) – The graph to extract subgraphs from.

• ntypes (list[str]) – The type names of the nodes in the subgraph.

Returns

G – The subgraph.

Return type

DGLGraph

Examples

The following example uses PyTorch backend.

>>> import dgl
>>> import torch


Instantiate a heterograph.

>>> g = dgl.heterograph({
>>>     ('user', 'plays', 'game'): ([0, 1, 1, 2], [0, 0, 2, 1]),
>>>     ('user', 'follows', 'user'): ([0, 1, 1], [1, 2, 2])
>>> })
>>> # Set node features
>>> g.nodes['user'].data['h'] = torch.tensor([[0.], [1.], [2.]])


Get subgraphs.

>>> sub_g = g.node_type_subgraph(['user'])
>>> print(sub_g)
Graph(num_nodes=3, num_edges=3,
ndata_schemes={'h': Scheme(shape=(1,), dtype=torch.float32)}
edata_schemes={})


Get the extracted node features.

>>> sub_g.nodes['user'].data['h']
tensor([[0.],
[1.],
[2.]])