Add attributes for quantile regression tree

Author: wschin

src/Microsoft.ML.FastTree/TreeEnsemble/QuantileRegressionTree.cs

@@ -2,6 +2,8 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
+using System;
+using System.Collections.Generic;
 using Microsoft.ML.Data;
 using Microsoft.ML.Internal.Utilities;
 using Microsoft.ML.Model;
@@ -91,6 +93,40 @@ public void SetLabelsDistribution(double[] labelsDistribution, double[] weights)
             _instanceWeights = weights;
         }
 
+        internal IReadOnlyList<IReadOnlyList<double>> ExtractLeafSamples()
+        {
+            var sampledLabelsBuffer = new List<List<double>>();
+            var sampleCountPerLeaf = _labelsDistribution.Length / NumLeaves;
+            for (int i = 0; i < NumLeaves; ++i)
+            {
+                var samplesPerLeaf = new List<double>();
+                var weightsPerLeaf = new List<double>();
+                for (int j = 0; j < sampleCountPerLeaf; ++j)
+                    samplesPerLeaf.Add(_labelsDistribution[i * sampleCountPerLeaf + j]);
+                sampledLabelsBuffer.Add(samplesPerLeaf);
+            }
+            return sampledLabelsBuffer;
+        }
+
+        internal IReadOnlyList<IReadOnlyList<double>> ExtractLeafSampleWeights()
+        {
+            var labelWeightsBuffer = new List<List<double>>();
+            var sampleCountPerLeaf = _labelsDistribution.Length / NumLeaves;
+            for (int i = 0; i < NumLeaves; ++i)
+            {
+                var weightsPerLeaf = new List<double>();
+                for (int j = 0; j < sampleCountPerLeaf; ++j)
+                {
+                    if (_instanceWeights != null)
+                        weightsPerLeaf.Add(_instanceWeights[i * sampleCountPerLeaf + j]);
+                    else
+                        weightsPerLeaf.Add(1.0);
+                }
+                labelWeightsBuffer.Add(weightsPerLeaf);
+            }
+            return labelWeightsBuffer;
+        }
+
         public override int SizeInBytes()
         {
             return base.SizeInBytes() + _labelsDistribution.SizeInBytes() + (_instanceWeights != null ? _instanceWeights.SizeInBytes() : 0);

src/Microsoft.ML.FastTree/TreeEnsemble/RegressionTree.cs

@@ -35,6 +35,9 @@ public class RegressionTreeView
         public IReadOnlyList<IReadOnlyList<int>> CategoricalSplitFeatureRanges => _tree.CategoricalSplitFeatureRanges;
         public ReadOnlySpan<double> LeafValues => _tree.LeafValues;
 
+        public IReadOnlyList<IReadOnlyList<double>> LeafSamples { get; }
+        public IReadOnlyList<IReadOnlyList<double>> LeafSampleWeights { get; }
+
         /// <summary>
         /// Number of leaves in the tree. Note that <see cref="NumLeaves"/> does not take non-leaf nodes into account.
         /// </summary>
@@ -55,6 +58,13 @@ public class RegressionTreeView
         internal RegressionTreeView(RegressionTree tree)
         {
             _tree = tree;
+            LeafSamples = null;
+            LeafSampleWeights = null;
+            if (tree is QuantileRegressionTree)
+            {
+                LeafSamples = ((QuantileRegressionTree)tree).ExtractLeafSamples();
+                LeafSampleWeights = ((QuantileRegressionTree)tree).ExtractLeafSampleWeights();
+            }
         }
     }