Here’s a way of creating sparse vectors in MLLib:
import org.apache.spark.mllib.linalg.Vectors
import org.apache.spark.rdd.RDD
val rdd = sc.textFile("A.txt").map(line => line.split(",")).
map(ary => (ary(0).toInt, ary(1).toInt, ary(2).toDouble))
val pairRdd: RDD[(Int, (Int, Int, Double))] = rdd.map(el => (el._1, el))
val create = (first: (Int, Int, Double)) => (Array(first._2), Array(first._3))
val combine = (head: (Array[Int], Array[Double]), tail: (Int, Int, Double)) =>
(head._1 :+ tail._2, head._2 :+ tail._3)
val merge = (a: (Array[Int], Array[Double]), b: (Array[Int], Array[Double])) =>
(a._1 ++ b._1, a._2 ++ b._2)
val A = pairRdd.combineByKey(create,combine,merge).map(el =>
Vectors.sparse(3,el._2._1,el._2._2))
If you have a separate file of b’s then you would need to manipulate this
slightly to join the b’s to the A RDD and then create LabeledPoints. I guess
there is a way of doing this using the newer ML interfaces but it’s not
particularly obvious to me how.
One point: In the example you give the b’s are exactly the same as col 2 in the
A matrix. I presume this is just a quick hacked together example because that
would give a trivial result.
-------------------------------------------------------------------------------
Robin East
Spark GraphX in Action Michael Malak and Robin East
Manning Publications Co.
http://www.manning.com/books/spark-graphx-in-action
<http://www.manning.com/books/spark-graphx-in-action>
> On 3 Nov 2016, at 18:12, im281 [via Apache Spark User List]
> <[email protected]> wrote:
>
> I would like to use it. But how do I do the following
> 1) Read sparse data (from text or database)
> 2) pass the sparse data to the linearRegression class?
>
> For example:
>
> Sparse matrix A
> row, column, value
> 0,0,.42
> 0,1,.28
> 0,2,.89
> 1,0,.83
> 1,1,.34
> 1,2,.42
> 2,0,.23
> 3,0,.42
> 3,1,.98
> 3,2,.88
> 4,0,.23
> 4,1,.36
> 4,2,.97
>
> Sparse vector b
> row, column, value
> 0,2,.89
> 1,2,.42
> 3,2,.88
> 4,2,.97
>
> Solve Ax = b???
>
>
>
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-----
Robin East
Spark GraphX in Action Michael Malak and Robin East
Manning Publications Co.
http://www.manning.com/books/spark-graphx-in-action
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