Github user sethah commented on a diff in the pull request:
https://github.com/apache/spark/pull/15831#discussion_r88530411
--- Diff:
mllib/src/main/scala/org/apache/spark/ml/feature/ChiSqSelector.scala ---
@@ -243,6 +244,42 @@ final class ChiSqSelectorModel private[ml] (
StructType(outputFields)
}
+ private def compress(features: Vector): Vector = {
+ features match {
+ case SparseVector(_, indices, values) =>
+ val newSize = selectedFeatures.length
+ val newValues = new ArrayBuilder.ofDouble
+ val newIndices = new ArrayBuilder.ofInt
+ var i = 0
+ var j = 0
+ var indicesIdx = 0
+ var filterIndicesIdx = 0
+ while (i < indices.length && j < newSize) {
+ indicesIdx = indices(i)
+ filterIndicesIdx = selectedFeatures(j)
+ if (indicesIdx == filterIndicesIdx) {
+ newIndices += j
+ newValues += values(i)
+ j += 1
+ i += 1
+ } else {
+ if (indicesIdx > filterIndicesIdx) {
+ j += 1
+ } else {
+ i += 1
+ }
+ }
+ }
+ Vectors.sparse(newSize, newIndices.result(), newValues.result())
+ case DenseVector(values) =>
+ val values = features.toArray
+ Vectors.dense(selectedFeatures.map(i => values(i)))
+ case other =>
--- End diff --
btw there is no reason to have this case since `Vector` is a sealed trait
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