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<title>MADlib: In-Out Degree</title>
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<div class="header">
  <div class="headertitle">
<div class="title">In-Out Degree<div class="ingroups"><a class="el" href="group__grp__graph.html">Graph</a> &raquo; <a class="el" href="group__grp__graph__measures.html">Measures</a></div></div>  </div>
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<div class="contents">
<div class="toc"><b>Contents</b> <ul>
<li>
<a href="#degrees">In-out degrees</a> </li>
<li>
<a href="#examples">Examples</a> </li>
</ul>
</div><p>This function computes the degree of each node. The node degree is the number of edges adjacent to that node. The node in-degree is the number of edges pointing in to the node and node out-degree is the number of edges pointing out of the node.</p>
<p><a class="anchor" id="degrees"></a></p><dl class="section user"><dt>In-out degrees</dt><dd><pre class="syntax">
graph_vertex_degrees(
    vertex_table,
    vertex_id,
    edge_table,
    edge_args,
    out_table,
    grouping_cols
)
</pre></dd></dl>
<p><b>Arguments</b> </p><dl class="arglist">
<dt>vertex_table </dt>
<dd><p class="startdd">TEXT. Name of the table containing the vertex data for the graph. Must contain the column specified in the 'vertex_id' parameter below.</p>
<p class="enddd"></p>
</dd>
<dt>vertex_id </dt>
<dd><p class="startdd">TEXT, default = 'id'. Name of the column in 'vertex_table' containing vertex ids. The vertex ids are of type INTEGER with no duplicates. They do not need to be contiguous.</p>
<p class="enddd"></p>
</dd>
<dt>edge_table </dt>
<dd><p class="startdd">TEXT. Name of the table containing the edge data. The edge table must contain columns for source vertex, destination vertex and edge weight. Column naming convention is described below in the 'edge_args' parameter.</p>
<p class="enddd"></p>
</dd>
<dt>edge_args </dt>
<dd><p class="startdd">TEXT. A comma-delimited string containing multiple named arguments of the form "name=value". The following parameters are supported for this string argument:</p><ul>
<li>src (INTEGER): Name of the column containing the source vertex ids in the edge table. Default column name is 'src'.</li>
<li>dest (INTEGER): Name of the column containing the destination vertex ids in the edge table. Default column name is 'dest'.</li>
<li>weight (FLOAT8): Name of the column containing the edge weights in the edge table. Default column name is 'weight'.</li>
</ul>
<p class="enddd"></p>
</dd>
<dt>out_table </dt>
<dd><p class="startdd">TEXT. Name of the table to store the result. It contains a row for every vertex of every group and has the following columns (in addition to the grouping columns):</p><ul>
<li>vertex: The id for the source vertex. Will use the input vertex column 'id' for column naming.</li>
<li>indegree: Number of incoming edges to the vertex.</li>
<li>outdegree: Number of outgoing edges from the vertex.</li>
</ul>
<p class="enddd"></p>
</dd>
<dt>grouping_cols </dt>
<dd>TEXT, default = NULL. List of columns used to group the input into discrete subgraphs. These columns must exist in the edge table. When this value is null, no grouping is used and a single result is generated.  </dd>
</dl>
<p><a class="anchor" id="examples"></a></p><dl class="section user"><dt>Examples</dt><dd></dd></dl>
<ol type="1">
<li>Create vertex and edge tables to represent the graph: <pre class="syntax">
DROP TABLE IF EXISTS vertex, edge;
CREATE TABLE vertex(
        id INTEGER,
        name TEXT
        );
CREATE TABLE edge(
        src_id INTEGER,
        dest_id INTEGER,
        edge_weight FLOAT8
        );
INSERT INTO vertex VALUES
(0, 'A'),
(1, 'B'),
(2, 'C'),
(3, 'D'),
(4, 'E'),
(5, 'F'),
(6, 'G'),
(7, 'H');
INSERT INTO edge VALUES
(0, 1, 1.0),
(0, 2, 1.0),
(0, 4, 10.0),
(1, 2, 2.0),
(1, 3, 10.0),
(2, 3, 1.0),
(2, 5, 1.0),
(2, 6, 3.0),
(3, 0, 1.0),
(4, 0, -2.0),
(5, 6, 1.0),
(6, 7, 1.0);
</pre></li>
<li>Calculate the in-out degrees for each node: <pre class="syntax">
DROP TABLE IF EXISTS degrees;
SELECT madlib.graph_vertex_degrees(
    'vertex',      -- Vertex table
    'id',          -- Vertix id column (NULL means use default naming)
    'edge',        -- Edge table
    'src=src_id, dest=dest_id, weight=edge_weight',
    'degrees');        -- Output table of shortest paths
SELECT * FROM degrees ORDER BY id;
</pre> <pre class="result">
 id | indegree | outdegree
----+----------+-----------
  0 |        2 |         3
  1 |        1 |         2
  2 |        2 |         3
  3 |        2 |         1
  4 |        1 |         1
  5 |        1 |         1
  6 |        2 |         1
  7 |        1 |         0
</pre></li>
<li>Create a graph with 2 groups and find degrees for each group: <pre class="syntax">
DROP TABLE IF EXISTS edge_gr;
CREATE TABLE edge_gr AS
(
  SELECT *, 0 AS grp FROM edge
  UNION
  SELECT *, 1 AS grp FROM edge WHERE src_id &lt; 6 AND dest_id &lt; 6
);
INSERT INTO edge_gr VALUES
(4,5,-20,1);
</pre></li>
<li>Find in-out degrees for all groups: <pre class="syntax">
DROP TABLE IF EXISTS out_gr;
SELECT madlib.graph_vertex_degrees(
    'vertex',      -- Vertex table
    NULL,          -- Vertex id column (NULL means use default naming)
    'edge_gr',     -- Edge table
    'src=src_id, dest=dest_id, weight=edge_weight',
    'out_gr',      -- Output table of shortest paths
    'grp'          -- Grouping columns
);
SELECT * FROM out_gr WHERE id &lt; 2 ORDER BY grp, id;
</pre> <pre class="result">
 grp | id | indegree |   outdegree
----&mdash;+---&mdash;+---------&mdash;+----------&mdash;
   0 |  0 |        2 |         3
   0 |  1 |        1 |         2
   1 |  0 |        2 |         3
   1 |  1 |        1 |         2
(4 rows)
</pre> </li>
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