[SPARK-10524] Decision tree binary classification with ordered categorical features: incorrect centroid

• Type: Bug
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 1.5.0, 1.6.0
• Fix Version/s: 1.6.1, 2.0.0
• Component/s: ML, MLlib
• Target Version/s: 1.6.1, 2.0.0
• Assignee: L. C. Hsieh
• Reporter: Joseph K. Bradley
• Shepherd: Joseph K. Bradley
• Created: 10/Sep/15 00:46
• Updated: 10/Feb/16 01:25
• Resolved: 10/Feb/16 01:13

Description

In DecisionTree and RandomForest binary classification with ordered categorical features, we order categories' bins based on the hard prediction, but we should use the soft prediction.

Here are the 2 places in mllib and ml:

• https://github.com/apache/spark/blob/45de518742446ddfbd4816c9d0f8501139f9bc2d/mllib/src/main/scala/org/apache/spark/mllib/tree/DecisionTree.scala#L887
• https://github.com/apache/spark/blob/45de518742446ddfbd4816c9d0f8501139f9bc2d/mllib/src/main/scala/org/apache/spark/ml/tree/impl/RandomForest.scala#L779

The PR which fixes this should include a unit test which isolates this issue, ideally by directly calling binsToBestSplit.

Issue Links

• links to: [Github] Pull Request #8734 (viirya)