The RDD you define has no particular ordering. So the order that you
encounter the elements ("rows") with an operation like take or collect
isn't defined. You can try to sort the RDD by the row number before
that key is discarded.
On Mon, Sep 29, 2014 at 2:58 PM, buring <qyqb...@gmail.com> wrote:
> Hi:
> I want to use SVD in my work. I tried some examples and have some
> confusions. The input the 4*3 matrix as follows:
> 2 0 0
> 0 3 2
> 0 3 1
> 2 0 3
> My input file text as follows which is corresponding to the matrix
> 0 0 2
> 1 1 3
> 1 2 2
> 2 2 1
> 2 1 3
> 3 0 2
> 3 2 3
> After run the svd algorithm ,I tried to reCompute the input matrix
> through
> U*S*V.T.But I found that ,The input matrix's row is not as expected,I
> printed it out:
> 2 0 0
> 0 3 1
> 0 3 2
> 2 0 3
> which rows 2 exchanged with rows 3,I confused on this.Can any one
> explain?
>
> My code is that :
> val inputData = sc.textFile(fname).map{
> line=>
> val parts = line.trim.split(' ')
> (parts(0).toLong,parts(1).toInt,parts(2).toDouble)
> }
>
> val dataRows = inputData.groupBy(_._1).map[(Long, Vector)]{ row =>
> val (indices, values) = row._2.map(e => (e._2, e._3)).unzip
> (row._1, new SparseVector(ncol, indices.toArray, values.toArray))
> }
> val data =
> dataRows.take(dataRows.count().toInt).map(e=>e._1+e._2.toArray.mkString(";"))
> logInfo("----------------")
> logInfo(data(0))
> logInfo(data(1))
> logInfo(data(2))
> logInfo(data(3))
>
> Here is the print code ,and this matrix is the same as the reCompute
> matrix U*S*V.T. But the order of rows has changed which I can't understand.I
> want to have the same matrix as the input file. How to guarantee this?
>
> Thanks！
>
>
>
> --
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>
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