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https://issues.apache.org/jira/browse/MAHOUT-1691?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14496804#comment-14496804
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Dmitriy Lyubimov commented on MAHOUT-1691:
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[~avati] that'd be nice in theory. that's exactly what R does. in practice, not
quite sure whether we can instrument any writing code, such as setQuick()
> iterable of vectors to matrix
> ------------------------------
>
> Key: MAHOUT-1691
> URL: https://issues.apache.org/jira/browse/MAHOUT-1691
> Project: Mahout
> Issue Type: Improvement
> Components: Math
> Affects Versions: 0.10.1
> Reporter: Alexey Grigorev
> Priority: Minor
> Labels: math, scala
>
> In Mahout scala bindings, instead of writing
> {code}
> val res = drmX.mapBlock(drmX.ncol) {
> case (keys, block) => {
> val copy = block.like
> copy := block.map(row => (row - mean) / std)
> (keys, copy)
> }
> }
> {code}
> I would like to be able to write
> {code}
> val res = drmX.mapBlock(drmX.ncol) {
> case (keys, block) => {
> keys -> block.map(row => (row - mean) / std)
> }
> }
> {code}
> Solution: add a method for implicit conversion from iterable to Matrix:
> {code}
> implicit def iterable2Matrix(that: Iterable[Vector]): Matrix = {
> val first = that.head
> val nrow = that.size
> val ncol = first.size
> val m = if (first.isDense) {
> new DenseMatrix(nrow, ncol)
> } else {
> new SparseRowMatrix(nrow, ncol)
> }
> that.zipWithIndex.foreach { case (row, idx) =>
> m.assignRow(idx.toInt, row)
> }
> m
> }
> {code}
> If it sounds nice, I can send a pull request with this implemented
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