graph小案例
（小案例，有五个人他们参见相亲节目，这个五个人分别是0,1,2,3,4,号选手，计算出追随者年龄大于被追随者年龄的人数和平均年龄）
scala> import org.apache.spark._
import org.apache.spark._
scala> import org.apache.spark.rdd.RDD
import org.apache.spark.rdd.RDD
scala> import org.apache.spark.graphx._
import org.apache.spark.graphx._
scala> import org.apache.spark.graphx.util._
import org.apache.spark.graphx.util._
创建graph
scala> var graphs =
GraphGenerators.logNormalGraph(sc, numVertices = 5).mapVertices( (id, _) => id.toDouble )
graphs: org.apache.spark.graphx.Graph[Double,Int] = org.apache.spark.graphx.impl.GraphImpl@1461f52d
GraphGenerators.logNormalGraph://生成一个图的顶点的出度分布是日志正常。
numVertices：生成5个顶点，也就是五个人
查看生成的graph
vertices
VertexId, Double)] = Array((4,4.0), (0,0.0), (1,1.0), (3,3.0), (2,2.0))
srcid attr srcid:选手编号 attr：年龄
0 0
1 1
2 2
3 3
4 4
edges
Array(Edge(0,1,1), Edge(0,1,1), Edge(0,3,1), Edge(0,4,1), Edge(1,2,1), Edge(1,4,1), Edge(2,0,1), Edge(2,0,1), Edge(2,3,1), Edge(2,4,1), Edge(3,3,1), Edge(4,0,1), Edge(4,3,1))
srcid dstid attr srcid:追随者 dstid:被追随者 attr:年龄
0 1 1
0 1 1
0 3 1
0 4 1
1 2 1
1 4 1
2 0 1
2 0 1
2 3 1
2 4 1
1 3 1
4 0 1
4 3 1
获取srcid>dstid的数据（把追随者年龄大于被追随者年龄的人，发送给被追随者）
scala> val olderFollowers: VertexRDD[(Int, Double)] = graphs.aggregateMessages[(Int, Double)](
| triplet => { // Map Function
| if (triplet.srcAttr > triplet.dstAttr) {
| // Send message to destination vertex containing counter and age
| triplet.sendToDst(1, triplet.srcAttr)
| }
| },
| // Add counter and age
| (a, b) => (a._1 + b._1, a._2 + b._2) // Reduce Function
| )
获取graphs的triplets,过滤出来srcAttr>srcDst的数据，并将结果发送给DstId
triplet.sendToDst(1, triplet.srcAttr)：中的1是一个计数器，
查看数据
res3: Array[(org.apache.spark.graphx.VertexId, (Int, Double))] = Array((0,(3,8.0)), (3,(1,4.0)))
(0,(3,8.0)：
0是srcId
3是srcId的入度
8.0是attr的和
计算出平均年龄
scala> val avgAgeOfOlderFollowers: VertexRDD[Double] =
| olderFollowers.mapValues( (id, value) =>
| value match { case (count, totalAge) => totalAge / count } )
avgAgeOfOlderFollowers: org.apache.spark.graphx.VertexRDD[Double] = VertexRDDImpl[48] at RDD at VertexRDD.scala:57
olderFollowers.mapValues：只对value进行操作
count是计数后的值
tatalAge:是attr的和
