pyspark GraphFrames 中的 Motifs答案

【问题标题】：Motifs in pyspark GraphFramespyspark GraphFrames 中的 Motifs
【发布时间】：2018-05-25 03:34:20
【问题描述】：

我是 pyspark 的新手，正在努力从 GraphFrame 中寻找主题。我得到的结果是空的，尽管我知道顶点和边之间存在关系这一事实。我在 Cloudera 上的 Jupyter 中使用 Spark 1.6 运行它。我的顶点和边（以及架构）的屏幕截图位于以下链接中：verticesRDD 和 edgesRDD

我正在阅读GraphFrames，但没有得到它......到目前为止我有以下代码。我哪里错了..？

#import relevant libraries for Graph Frames
from pyspark import SparkContext
from pyspark.sql import SQLContext
from pyspark.sql.functions import desc
from graphframes import *

#Read the csv files 
verticesRDD = sqlContext.read.format("com.databricks.spark.csv").options(header='true', inferschema='true').load("filepath/station.csv")
edgesRDD = sqlContext.read.format("com.databricks.spark.csv").options(header='true', inferschema='true').load("filepath/trip.csv")

#Renaming the id columns to enable GraphFrame 
verticesRDD = verticesRDD.withColumnRenamed("station_ID", "id")
edgesRDD = edgesRDD.withColumnRenamed("Trip ID", "id")
edgesRDD = edgesRDD.withColumnRenamed("Start Station", "src")
edgesRDD = edgesRDD.withColumnRenamed("End Station", "dst")

#Register as temporary tables for running the analysis
verticesRDD.registerTempTable("verticesRDD")
edgesRDD.registerTempTable("edgesRDD")
#Note: whether i register the RDDs as temp tables or not, i get the same epty results... so im not sure if this step is really needed

#Make the GraphFrame
g = GraphFrame(verticesRDD, edgesRDD)

print g
#this deisplays the following:
#GraphFrame(v:[id: int, name: string, lat: double, long: double, dockcount: int, landmark: string, installation: string], e:[src: string, dst: string, id: int, Duration: int, Start Date: string, Start Terminal: int, End Date: string, End Terminal: int, Bike #: int, Subscriber Type: string, Zip Code: string])

#Stations where a is connected to b
motifs = g.find("(a)-[e1]->(b)")
motifs.show()

+---+---+---+
| e1|  a|  b|
+---+---+---+
+---+---+---+

motifs = g.find("(a)-[e1]->(b); (b)-[e2]->(a)")
motifs.show()

+---+---+---+---+
| e1|  a|  b| e2|
+---+---+---+---+
+---+---+---+---+


motifs = g.find("(a)-[e1]->(b); (b)-[e2]->(c)")
motifs.show()

+---+---+---+---+---+
| e1|  a|  b| e2|  c|
+---+---+---+---+---+
+---+---+---+---+---+

#Stations where a is connected to b, b is connected to c 
#but c is not connected to a
motifs = g.find("(a)-[e1]->(b); (b)-[e2]->(c)").filter("(c!=a)")
motifs.show()

+---+---+---+---+---+
| e1|  a|  b| e2|  c|
+---+---+---+---+---+
+---+---+---+---+---+

【问题讨论】：

标签： pyspark pyspark-sql graphframes

【解决方案1】：

问题在于我是如何定义顶点的。我正在将“station_id”重命名为“id”，而事实上，它必须是“name。所以这一行

verticesRDD = verticesRDD.withColumnRenamed("station_ID", "id")

必须是

verticesRDD = verticesRDD.withColumnRenamed("name", "id")

Motifs 与此更改一起正常工作！

【讨论】：