Github user mengxr commented on a diff in the pull request:
https://github.com/apache/spark/pull/1814#discussion_r15920617
--- Diff: mllib/src/main/scala/org/apache/spark/mllib/feature/IDF.scala ---
@@ -177,18 +115,72 @@ private object IDF {
private def isEmpty: Boolean = m == 0L
/** Returns the current IDF vector. */
- def idf(): BDV[Double] = {
+ def idf(): Vector = {
if (isEmpty) {
throw new IllegalStateException("Haven't seen any document yet.")
}
val n = df.length
- val inv = BDV.zeros[Double](n)
+ val inv = new Array[Double](n)
var j = 0
while (j < n) {
inv(j) = math.log((m + 1.0)/ (df(j) + 1.0))
j += 1
}
- inv
+ Vectors.dense(inv)
}
}
}
+
+/**
+ * :: Experimental ::
+ * Represents an IDF model that can transform term frequency vectors.
+ */
+@Experimental
+class IDFModel private[mllib] (val idf: Vector) extends Serializable {
+
+ /**
+ * Transforms term frequency (TF) vectors to TF-IDF vectors.
+ * @param dataset an RDD of term frequency vectors
+ * @return an RDD of TF-IDF vectors
+ */
+ def transform(dataset: RDD[Vector]): RDD[Vector] = {
+ val bcIdf = dataset.context.broadcast(idf)
+ dataset.mapPartitions { iter =>
+ val thisIdf = bcIdf.value
+ iter.map { v =>
+ val n = v.size
+ v match {
+ case sv: SparseVector =>
+ val nnz = sv.indices.size
+ val newValues = new Array[Double](nnz)
+ var k = 0
+ while (k < nnz) {
+ newValues(k) = sv.values(k) * thisIdf(sv.indices(k))
+ k += 1
+ }
+ Vectors.sparse(n, sv.indices, newValues)
+ case dv: DenseVector =>
+ val newValues = new Array[Double](n)
+ var j = 0
+ while (j < n) {
+ newValues(j) = dv.values(j) * thisIdf(j)
+ j += 1
+ }
+ Vectors.dense(newValues)
+ case other =>
+ throw new UnsupportedOperationException(
--- End diff --
We might want to use different error messages. In that case, having a util
function doesn't save us much.
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