chain_struct

Scilab function
Last update : September 1996

chain_struct - chained structure from adjacency lists of a graph

### Calling Sequence

  `[fe,che,fn,chn] = chain_struct(g)`
  `[fe,che,fn,chn] = chain_struct(lp,la,ls)`

### Parameters

- `g` : graph list
- `lp` : row vector, pointer array of the adjacency lists description of the graph (its size is the number of nodes of the graph + 1)
- `la` : row vector, arc array of the adjacency lists description of the graph (its size is the number of edges of the graph)
- `ls` : row vector, node array of the adjacency lists description of the graph (its size is the number of edges of the graph)
- `fe` : row vector of the numbers of the first edges starting from nodes (its size is the number of nodes of the graph)
- `che` : row vector of the numbers of the chained edges (its size is the number of edges of the graph)
- `fn` : row vector of the numbers of the first nodes reached by the edges of `fe` (its size is the number of nodes of the graph)
- `chn` : row vector of the nodes reached by the edges of `che`

### Description

`chain_struct` computes the row vectors of the edge chained structure description of the graph `g` . It is also possible to give directly `chain_struct` the adjacency lists of the graph. This is more efficient if the adjacency lists are already available since `chain_struct` uses them to make computations.

The vectors `fe` , `che` , `fn` and `chn` describe the chained structure in the following way:

`fe(i))` is the number of the first edge starting from node i

`che(fe(i))` is the number of the second edge starting from node i, `che(che(fe(i)))` is the number of the third edge starting from node i and so on until the value is 0

`fn(i)` is the number of the first node reached from node i

`ch(i)` is the number of the node reached by edge `che(i)` .

### Examples

    ta=[1 1 2 3 5 4 6 7 7 3 3 8 8 5];
    he=[2 3 5 4 6 6 7 4 3 2 8 1 7 4];
    g=make_graph('foo',1,8,ta,he);
    g('node_x')=[116 231 192 323 354 454 305 155];
    g('node_y')=[118 116 212 219 117 185 334 316];
    show_graph(g);
    [fe,che,fn,chn] = chain_struct(g)

### See Also

`adj_lists` , `graph_2_mat` ,