Github user jkbradley commented on a diff in the pull request:
https://github.com/apache/spark/pull/5330#discussion_r28208664
--- Diff:
mllib/src/main/scala/org/apache/spark/mllib/tree/model/treeEnsembleModels.scala
---
@@ -166,6 +150,65 @@ class GradientBoostedTreesModel(
object GradientBoostedTreesModel extends Loader[GradientBoostedTreesModel]
{
+ /**
+ * Compute the initial predictions and errors for a dataset for the first
+ * iteration of gradient boosting.
+ * @param Training data.
+ * @param initTreeWeight: learning rate assigned to the first tree.
+ * @param initTree: first DecisionTreeModel.
+ * @param loss: evaluation metric.
+ * @return a RDD with each element being a zip of the prediction and
error
+ * corresponding to every sample.
+ */
+ def computeInitialPredictionAndError(
+ data: RDD[LabeledPoint],
+ initTreeWeight: Double,
+ initTree: DecisionTreeModel,
+ loss: Loss): RDD[(Double, Double)] = {
+ data.map { lp =>
+ val pred = initTreeWeight * initTree.predict(lp.features)
+ val error = loss.computeError(pred, lp.label)
+ (pred, error)
+ }
+ }
+
+ /**
+ * Update a zipped predictionError RDD
+ * (as obtained with computeInitialPredictionAndError)
+ * @param training data.
+ * @param predictionAndError: predictionError RDD
+ * @param nTree: tree index.
--- End diff --
"nTree" no longer exists
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