From 80e4d98dc656e20dacbd8cdbf92d4912673b42ae Mon Sep 17 00:00:00 2001
From: "Joseph E. Gonzalez" <joseph.e.gonzalez@gmail.com>
Date: Mon, 13 Jan 2014 13:40:16 -0800
Subject: Improving documentation and identifying potential bug in CC
 calculation.

---
 docs/graphx-programming-guide.md | 33 +++++++++++++++++++++++++++------
 1 file changed, 27 insertions(+), 6 deletions(-)

(limited to 'docs/graphx-programming-guide.md')

diff --git a/docs/graphx-programming-guide.md b/docs/graphx-programming-guide.md
index 2697b2def7..ed976b8989 100644
--- a/docs/graphx-programming-guide.md
+++ b/docs/graphx-programming-guide.md
@@ -84,7 +84,8 @@ import org.apache.spark.graphx._
 import org.apache.spark.rdd.RDD
 {% endhighlight %}
 
-If you are not using the Spark shell you will also need a Spark context.
+If you are not using the Spark shell you will also need a `SparkContext`.  To learn more about
+getting started with Spark refer to the [Spark Quick Start Guide](quick-start.html).
 
 # The Property Graph
 <a name="property_graph"></a>
@@ -190,7 +191,7 @@ and `graph.edges` members respectively.
 {% highlight scala %}
 val graph: Graph[(String, String), String] // Constructed from above
 // Count all users which are postdocs
-graph.vertices.filter { case (id, (name, pos)) => pos == "postdoc"}.count
+graph.vertices.filter { case (id, (name, pos)) => pos == "postdoc" }.count
 // Count all the edges where src > dst
 graph.edges.filter(e => e.srcId > e.dstId).count
 {% endhighlight %}
@@ -258,8 +259,10 @@ val graph: Graph[(String, String), String]
 val indDegrees: VertexRDD[Int] = graph.inDegrees
 {% endhighlight %}
 
-The reason for differentiating between core graph operations and GraphOps is to be able to support
-various graph representations in the future.
+The reason for differentiating between core graph operations and [`GraphOps`][GraphOps] is to be
+able to support different graph representations in the future.  Each graph representation must
+provide implementations of the core operations and reuse many of the useful operations defined in
+[`GraphOps`][GraphOps].
 
 ## Property Operators
 
@@ -334,14 +337,32 @@ interest or eliminate broken links. For example in the following code we remove
 [Graph.subgraph]: api/graphx/index.html#org.apache.spark.graphx.Graph@subgraph((EdgeTriplet[VD,ED])⇒Boolean,(VertexID,VD)⇒Boolean):Graph[VD,ED]
 
 {% highlight scala %}
-val users: RDD[(VertexId, (String, String))]
-val edges: RDD[Edge[String]]
+// Create an RDD for the vertices
+val users: RDD[(VertexID, (String, String))] =
+  sc.parallelize(Array((3L, ("rxin", "student")), (7L, ("jgonzal", "postdoc")),
+                       (5L, ("franklin", "prof")), (2L, ("istoica", "prof")),
+                       (4L, ("peter", "student"))))
+// Create an RDD for edges
+val relationships: RDD[Edge[String]] =
+  sc.parallelize(Array(Edge(3L, 7L, "collab"),    Edge(5L, 3L, "advisor"),
+                       Edge(2L, 5L, "colleague"), Edge(5L, 7L, "pi"),
+                       Edge(4L, 0L, "student"),   Edge(5L, 0L, "colleague")))
 // Define a default user in case there are relationship with missing user
 val defaultUser = ("John Doe", "Missing")
 // Build the initial Graph
 val graph = Graph(users, relationships, defaultUser)
+// Notice that there is a user 0 (for which we have no information) connecting users
+// 4 (peter) and 5 (franklin).
+graph.triplets.map(
+    triplet => triplet.srcAttr._1 + " is the " + triplet.attr + " of " + triplet.dstAttr._1
+  ).collect.foreach(println(_))
 // Remove missing vertices as well as the edges to connected to them
 val validGraph = graph.subgraph(vpred = (id, attr) => attr._2 != "Missing")
+// The valid subgraph will disconnect users 4 and 5 by removing user 0
+validGraph.vertices.collect.foreach(println(_))
+validGraph.triplets.map(
+    triplet => triplet.srcAttr._1 + " is the " + triplet.attr + " of " + triplet.dstAttr._1
+  ).collect.foreach(println(_))
 {% endhighlight %}
 
 > Note in the above example only the vertex predicate is provided.  The `subgraph` operator defaults
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