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I am new to pyspark and am struggling with finding motifs from a GraphFrame. I am getting empty results, though I know for a fact that relationships exist between the vertices and edges. I am running this with Spark 1.6 in Jupyter on Cloudera. Screenshots of my vertices and edges (as well as the schema) are in these links: verticesRDD and edgesRDD

I am reading GraphFrames but not getting it... I have the following code so far. Where am i going wrong..?

#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|
+---+---+---+---+---+
+---+---+---+---+---+
vikram
  • 21
  • 1

1 Answers1

2

The problem was how I was defining my vertices. I was renaming "station_id" to "id", when in fact, it had to be "name. So this line

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

has to be be

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

Motifs working properly with this change!

vikram
  • 21
  • 1