# Extract subgraph using names

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IrisL on 25 Aug 2022
Answered: Steven Lord on 25 Aug 2022
Hi MathWorks community,
I have a graph G which has 6119 nodes. I want to extract a subgraph H with only 539 nodes. The name of the nodes that need to be extract are in a seperate 539 x 1 double called NodeID. I tried the following code, but received 'Error using graph/subgraph (line 29) Nodes must be a vector of unique node indices, a vector of unique node names, or a logical vector of length equal to the number of nodes.'.
H = subgraph(G,strtrim(num2str(NodeID)))
I am not sure what the problem is and what should I do to resolve the problem.
For your reference, I am also attaching my G.Nodes and NodeID as a mat. file.
Thanks!
##### 2 CommentsShowHide 1 older comment
IrisL on 25 Aug 2022
Thanks. Just edit my post.

Steven Lord on 25 Aug 2022
I'd use a string array, both when naming the nodes initially and when extracting the subgraph.
B = bucky;
n = height(B);
G = graph(B, string(1:n))
G =
graph with properties: Edges: [90×2 table] Nodes: [60×1 table]
nodeIDs = randperm(n, n/4) % Extract 1/4 of the nodes
nodeIDs = 1×15
5 25 43 55 4 13 7 44 54 14 33 22 17 35 59
G2 = subgraph(G, string(nodeIDs))
G2 =
graph with properties: Edges: [5×2 table] Nodes: [15×1 table]
figure
plot(G)
title('Bucky')
figure
plot(G2)
title('Bucky/4')

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