Implementing copy column estimator

src/Microsoft.ML.Data/EntryPoints/SchemaManipulation.cs

@@ -48,8 +48,7 @@ public static CommonOutputs.TransformOutput CopyColumns(IHostEnvironment env, Co
             var host = env.Register("CopyColumns");
             host.CheckValue(input, nameof(input));
             EntryPointUtils.CheckInputArgs(host, input);
-
-            var xf = new CopyColumnsTransform(env, input, input.Data);
+            var xf = CopyColumnsTransform.Create(env, input, input.Data);
             return new CommonOutputs.TransformOutput { Model = new TransformModel(env, xf, input.Data), OutputData = xf };
         }
 

src/Microsoft.ML.Data/EntryPoints/ScoreColumnSelector.cs

@@ -26,9 +26,8 @@ public static CommonOutputs.TransformOutput SelectColumns(IHostEnvironment env,
             Contracts.CheckValue(env, nameof(env));
             env.CheckValue(input, nameof(input));
             EntryPointUtils.CheckInputArgs(env, input);
-            int colMax;
             var view = input.Data;
-            var maxScoreId = view.Schema.GetMaxMetadataKind(out colMax, MetadataUtils.Kinds.ScoreColumnSetId);
+            var maxScoreId = view.Schema.GetMaxMetadataKind(out int colMax, MetadataUtils.Kinds.ScoreColumnSetId);
             List<int> indices = new List<int>();
             for (int i = 0; i < view.Schema.ColumnCount; i++)
             {
@@ -82,7 +81,7 @@ public static CommonOutputs.TransformOutput RenameBinaryPredictionScoreColumns(I
                     // Rename all the score columns.
                     int colMax;
                     var maxScoreId = input.Data.Schema.GetMaxMetadataKind(out colMax, MetadataUtils.Kinds.ScoreColumnSetId);
-                    var copyCols = new List<CopyColumnsTransform.Column>();
+                    var copyCols = new List<(string Source, string Name)>();
                     for (int i = 0; i < input.Data.Schema.ColumnCount; i++)
                     {
                         if (input.Data.Schema.IsHidden(i))
@@ -99,10 +98,10 @@ public static CommonOutputs.TransformOutput RenameBinaryPredictionScoreColumns(I
                         }
                         var source = input.Data.Schema.GetColumnName(i);
                         var name = source + "." + positiveClass;
-                        copyCols.Add(new CopyColumnsTransform.Column() { Name = name, Source = source });
+                        copyCols.Add((source, name));
                     }
 
-                    var copyColumn = new CopyColumnsTransform(env, new CopyColumnsTransform.Arguments() { Column = copyCols.ToArray() }, input.Data);
+                    var copyColumn = new CopyColumnsTransform(env, copyCols.ToArray()).Transform(input.Data);
                     var dropColumn = new DropColumnsTransform(env, new DropColumnsTransform.Arguments() { Column = copyCols.Select(c => c.Source).ToArray() }, copyColumn);
                     return new CommonOutputs.TransformOutput { Model = new TransformModel(env, dropColumn, input.Data), OutputData = dropColumn };
                 }

src/Microsoft.ML.Data/Evaluators/MulticlassClassifierEvaluator.cs

@@ -925,18 +925,7 @@ protected override IDataView GetOverallResultsCore(IDataView overall)
 
         private IDataView ChangeTopKAccColumnName(IDataView input)
         {
-            var cpyArgs = new CopyColumnsTransform.Arguments
-            {
-                Column = new[]
-                {
-                    new CopyColumnsTransform.Column()
-                    {
-                        Name=string.Format(TopKAccuracyFormat, _outputTopKAcc),
-                        Source=MultiClassClassifierEvaluator.TopKAccuracy
-                    }
-                }
-            };
-            input = new CopyColumnsTransform(Host, cpyArgs, input);
+            input = new CopyColumnsTransform(Host, (MultiClassClassifierEvaluator.TopKAccuracy, string.Format(TopKAccuracyFormat, _outputTopKAcc))).Transform(input);
             var dropArgs = new DropColumnsTransform.Arguments
             {
                 Column = new[] { MultiClassClassifierEvaluator.TopKAccuracy }