ch05 - potentially unexpected result from sample code about aas

[srowen]

I think you're right; this should really be aggregate? that is it needs to handle adding together the current sum of squares, and the square of a new value, differently from summing partial sums of squares?

    val sumSquares = dataAsArray.aggregate(
        new Array[Double](numCols)
      )(
        (a, b) => a.zip(b).map(t => t._1 + t._2 * t._2),
        (a, b) => a.zip(b).map(t => t._1 + t._2)
      )

[srowen]

Resolved in source and filed as an erratum.

[dolaameng]

Another way might be just using stats(), even though I think its a little bit slower. The book is a great work. Thanks!

[srowen]

Fair enough, yes; I kind of wanted to show computing these things directly in an FP-oriented way.