火花图形框架有状态主题

Question

图形框架有一个很好的有状态基元的例子。如何显式返回计数？如您所见，输出仅包含顶点和朋友，但不包含计数。

如何修改它以不仅（不仅）可以访问边，还可以访问顶点的标签？

when(relationship === "friend", cnt + 1).otherwise(cnt)

即我怎样才能增加计数

• 年龄> 30 的每个顶点的朋友

• 好友百分比大于30/全部好友

  val g = examples.Graphs.friends  // get example graph
  // Find chains of 4 vertices.
  val chain4 = g.find("(a)-[ab]->(b); (b)-[bc]->(c); (c)-[cd]->(d)")
  // Query on sequence, with state (cnt)
  //  (a) Define method for updating state given the next element of the motif.
  def sumFriends(cnt: Column, relationship: Column): Column = {
    when(relationship === "friend", cnt + 1).otherwise(cnt)
  }
  //  (b) Use sequence operation to apply method to sequence of elements in motif.
  //      In this case, the elements are the 3 edges.
  val condition = Seq("ab", "bc", "cd").
    foldLeft(lit(0))((cnt, e) => sumFriends(cnt, col(e)("relationship")))
  //  (c) Apply filter to DataFrame.
  val chainWith2Friends2 = chain4.where(condition >= 2)
  

  http://graphframes.github.io/user-guide.html

  chainWith2Friends2.show()
  

哪个将输出

+-------------+------------+-------------+------------+-------------+------------+--------------+
|            a|          ab|            b|          bc|            c|          cd|             d|
+-------------+------------+-------------+------------+-------------+------------+--------------+
|[e,Esther,32]|[e,d,friend]| [d,David,29]|[d,a,friend]| [a,Alice,34]|[a,e,friend]| [e,Esther,32]|
|[e,Esther,32]|[e,d,friend]| [d,David,29]|[d,a,friend]| [a,Alice,34]|[a,b,friend]|    [b,Bob,36]|
| [d,David,29]|[d,a,friend]| [a,Alice,34]|[a,e,friend]|[e,Esther,32]|[e,d,friend]|  [d,David,29]|
| [d,David,29]|[d,a,friend]| [a,Alice,34]|[a,e,friend]|[e,Esther,32]|[e,f,follow]|  [f,Fanny,36]|
| [d,David,29]|[d,a,friend]| [a,Alice,34]|[a,b,friend]|   [b,Bob,36]|[b,c,follow]|[c,Charlie,30]|
| [a,Alice,34]|[a,e,friend]|[e,Esther,32]|[e,d,friend]| [d,David,29]|[d,a,friend]|  [a,Alice,34]|
+-------------+------------+-------------+------------+-------------+------------+--------------+

Answer 1

请注意，sumFriends返回一个列，因此condition列是一列。这就是为什么您可以在不带引号的where语句中访问它的原因。因此，您所要做的就是将该列添加到数据帧中。运行上面的代码后，我可以运行

chain4.withColumn("condition",condition).select("condition").show
+---------+ 
|condition|
+---------+
 | 1|
 | 0|
 | 0|
 | 0|
 | 0|
 | 3|
 | 3|
 | 3|
 | 2|
 | 2|
 | 3|
 | 1|
+---------+

您也可以使用chain4.select(condition)

希望这有帮助