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From salexln <sale...@gmail.com>
Subject RDD[Vector] Immutability issue
Date Mon, 28 Dec 2015 20:36:33 GMT
Hi guys,
I know the RDDs are immutable and therefore their value cannot be changed
but I see the following behaviour:
I wrote an implementation for FuzzyCMeans algorithm and now I'm testing it,
so i run the following example:

import org.apache.spark.mllib.clustering.FuzzyCMeans
import org.apache.spark.mllib.linalg.Vectors

val data =
sc.textFile("/home/development/myPrjects/R/butterfly/butterfly.txt")
val parsedData = data.map(s => Vectors.dense(s.split('
').map(_.toDouble))).cache()
> parsedData: org.apache.spark.rdd.RDD[org.apache.spark.mllib.linalg.Vector]
> = MapPartitionsRDD[2] at map at <console>:31

val numClusters = 2
val numIterations = 20

parsedData.foreach{ point => println(point) } 
> [0.0,-8.0]
[-3.0,-2.0]
[-3.0,0.0]
[-3.0,2.0]
[-2.0,-1.0]
[-2.0,0.0]
[-2.0,1.0]
[-1.0,0.0]
[0.0,0.0]
[1.0,0.0]
[2.0,-1.0]
[2.0,0.0]
[2.0,1.0]
[3.0,-2.0]
[3.0,0.0]
[3.0,2.0]
[0.0,8.0]

val clusters = FuzzyCMeans.train(parsedData, numClusters, numIteration
parsedData.foreach{ point => println(point) } 
> 
[0.0,-0.4803333185624595]
[-0.1811743096972924,-0.12078287313152826]
[-0.06638890786148487,0.0]
[-0.04005925925925929,0.02670617283950619]
[-0.12193263222069807,-0.060966316110349035]
[-0.0512,0.0]
[NaN,NaN]
[-0.049382716049382706,0.0]
[NaN,NaN]
[0.006830134553650707,0.0]
[0.05120000000000002,-0.02560000000000001]
[0.04755220304297078,0.0]
[0.06581619798335057,0.03290809899167529]
[0.12010867103812725,-0.0800724473587515]
[0.10946638900458144,0.0]
[0.14814814814814817,0.09876543209876545]
[0.0,0.49119985188436205]



But how can this be that my method changes the Immutable RDD?

BTW, the signature of the train method, is the following:

train( data: RDD[Vector], clusters: Int, maxIterations: Int)




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