MATLAB: Re-indexing matrix which corresponds to mesh

indexingmatrix manipulationmesh

Hello
I'm wondering if anyone can help me. I'm trying to re-index two matrixes. I have selected a sub-sample of data and I need them to be re-numbered to 1:N. There is a corresponding matrix which is an Mx3 matrix which makes up the triangles.
I need to re-number the first matrax and then apply that re-numbered matrix to the list of triangles. This cannot be done by simple indexing because the numbers in the original matrix are obviously changed so they do not correspond with values in the 2nd matrix.
I'm not sure if I've explained that well but here is an example of the matrices I currently have.
I would also like to point out that those are just a sample number, the nodes may not necessarily match up below but they do in my matrices.
Cheers 🙂
Nodes:
3772
3947
3948
3949
4144
4145
4146
4147
4148
4149
Tri:
3771  3772  3603
3604  3603  3772
3773  3604  3772
3771  3946  3947
3948  3771  3947
3771  3948  3772
3772  3948  3949
3772  3949  3950
3772  3950  3773
3947  3946  4143

Best Answer

Let nodes and tri be your Nodes and Triangles.
[val,idx] = unique(nodes) ;
nodes_1 = nodes ;
tri_1 = tri ;
for i = 1:length(val)
    nodes_1(nodes==val(i))=i ;
    tri_1(tri==val(i)) = i ;
end
tri_1 and nodes_1 are the Nodes and Triangles re-indexed to 1:N.
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