Fix CategoricalHashTransform to handle OutputKind "Key" (#2017)

* Handle key output kind

* internal constructor

Author: Ivanidzo4ka

src/Microsoft.ML.Transforms/OneHotEncoding.cs

@@ -144,7 +144,7 @@ internal static IDataTransform Create(IHostEnvironment env, Arguments args, IDat
 
         private readonly TransformerChain<ITransformer> _transformer;
 
-        public OneHotEncodingTransformer(ValueToKeyMappingEstimator term, IEstimator<ITransformer> toVector, IDataView input)
+        internal OneHotEncodingTransformer(ValueToKeyMappingEstimator term, IEstimator<ITransformer> toVector, IDataView input)
         {
             if (toVector != null)
                 _transformer = term.Append(toVector).Fit(input);
@@ -189,7 +189,7 @@ public class ColumnInfo : ValueToKeyMappingTransformer.ColumnInfo
             /// <param name="sort">How items should be ordered when vectorized. If <see cref="ValueToKeyMappingTransformer.SortOrder.Occurrence"/> choosen they will be in the order encountered.
             /// If <see cref="ValueToKeyMappingTransformer.SortOrder.Value"/>, items are sorted according to their default comparison, for example, text sorting will be case sensitive (for example, 'A' then 'Z' then 'a').</param>
             /// <param name="term">List of terms.</param>
-            public ColumnInfo(string input, string output=null,
+            public ColumnInfo(string input, string output = null,
                 OneHotEncodingTransformer.OutputKind outputKind = Defaults.OutKind,
                 int maxNumTerms = ValueToKeyMappingEstimator.Defaults.MaxNumTerms, ValueToKeyMappingTransformer.SortOrder sort = ValueToKeyMappingEstimator.Defaults.Sort,
                 string[] term = null)
@@ -268,7 +268,13 @@ public OneHotEncodingEstimator(IHostEnvironment env, ColumnInfo[] columns,
             }
         }
 
-        public SchemaShape GetOutputSchema(SchemaShape inputSchema) => _term.Append(_toSomething).GetOutputSchema(inputSchema);
+        public SchemaShape GetOutputSchema(SchemaShape inputSchema)
+        {
+            if (_toSomething != null)
+                return _term.Append(_toSomething).GetOutputSchema(inputSchema);
+            else
+                return _term.GetOutputSchema(inputSchema);
+        }
 
         public OneHotEncodingTransformer Fit(IDataView input) => new OneHotEncodingTransformer(_term, _toSomething, input);
 

src/Microsoft.ML.Transforms/OneHotHashEncoding.cs

@@ -177,8 +177,10 @@ internal static IDataTransform Create(IHostEnvironment env, Arguments args, IDat
 
         internal OneHotHashEncoding(HashingEstimator hash, IEstimator<ITransformer> keyToVector, IDataView input)
         {
-            var chain = hash.Append(keyToVector);
-            _transformer = chain.Fit(input);
+            if (keyToVector != null)
+                _transformer = hash.Append(keyToVector).Fit(input);
+            else
+                _transformer = new TransformerChain<ITransformer>(hash.Fit(input));
         }
 
         public Schema GetOutputSchema(Schema inputSchema) => _transformer.GetOutputSchema(inputSchema);
@@ -312,7 +314,13 @@ public OneHotHashEncodingEstimator(IHostEnvironment env, params ColumnInfo[] col
             }
         }
 
-        public SchemaShape GetOutputSchema(SchemaShape inputSchema) => _hash.Append(_toSomething).GetOutputSchema(inputSchema);
+        public SchemaShape GetOutputSchema(SchemaShape inputSchema)
+        {
+            if (_toSomething != null)
+                return _hash.Append(_toSomething).GetOutputSchema(inputSchema);
+            else
+                return _hash.GetOutputSchema(inputSchema);
+        }
 
         public OneHotHashEncoding Fit(IDataView input) => new OneHotHashEncoding(_hash, _toSomething, input);
     }

test/Microsoft.ML.Tests/Transformers/CategoricalTests.cs

@@ -72,7 +72,27 @@ public void CategoricalOneHotHashEncoding()
             var mlContext = new MLContext();
             var dataView = ComponentCreation.CreateDataView(mlContext, data);
 
-            var pipe = mlContext.Transforms.Categorical.OneHotHashEncoding("A", "CatA", 16, 0, OneHotEncodingTransformer.OutputKind.Bag);
+            var pipe = mlContext.Transforms.Categorical.OneHotHashEncoding("A", "CatA", 3, 0, OneHotEncodingTransformer.OutputKind.Bag)
+                .Append(mlContext.Transforms.Categorical.OneHotHashEncoding("A", "CatB", 2, 0, OneHotEncodingTransformer.OutputKind.Key))
+                .Append(mlContext.Transforms.Categorical.OneHotHashEncoding("A", "CatC", 3, 0, OneHotEncodingTransformer.OutputKind.Ind))
+                .Append(mlContext.Transforms.Categorical.OneHotHashEncoding("A", "CatD", 2, 0, OneHotEncodingTransformer.OutputKind.Bin));
+
+            TestEstimatorCore(pipe, dataView);
+            Done();
+        }
+
+        [Fact]
+        public void CategoricalOneHotEncoding()
+        {
+            var data = new[] { new TestClass() { A = 1, B = 2, C = 3, }, new TestClass() { A = 4, B = 5, C = 6 } };
+
+            var mlContext = new MLContext();
+            var dataView = ComponentCreation.CreateDataView(mlContext, data);
+
+            var pipe = mlContext.Transforms.Categorical.OneHotEncoding("A", "CatA", OneHotEncodingTransformer.OutputKind.Bag)
+                .Append(mlContext.Transforms.Categorical.OneHotEncoding("A", "CatB", OneHotEncodingTransformer.OutputKind.Key))
+                .Append(mlContext.Transforms.Categorical.OneHotEncoding("A", "CatC", OneHotEncodingTransformer.OutputKind.Ind))
+                .Append(mlContext.Transforms.Categorical.OneHotEncoding("A", "CatD", OneHotEncodingTransformer.OutputKind.Bin));
 
             TestEstimatorCore(pipe, dataView);
             Done();
@@ -105,7 +125,7 @@ public void CategoricalStatic()
             {
                 var saver = new TextSaver(Env, new TextSaver.Arguments { Silent = true });
                 var savedData = TakeFilter.Create(Env, est.Fit(data).Transform(data).AsDynamic, 4);
-                var view = new ColumnSelectingTransformer(Env, new string[]{"A", "B", "C", "D", "E" }, null, false).Transform(savedData);
+                var view = new ColumnSelectingTransformer(Env, new string[] { "A", "B", "C", "D", "E" }, null, false).Transform(savedData);
                 using (var fs = File.Create(outputPath))
                     DataSaverUtils.SaveDataView(ch, saver, view, fs, keepHidden: true);
             }
@@ -198,13 +218,13 @@ private void ValidateMetadata(IDataView result)
             Assert.True(column.IsNormalized());
 
             column = result.Schema["CatG"];
-            Assert.Equal(column.Metadata.Schema.Select(x => x.Name), new string[1] { MetadataUtils.Kinds.KeyValues});
+            Assert.Equal(column.Metadata.Schema.Select(x => x.Name), new string[1] { MetadataUtils.Kinds.KeyValues });
             column.Metadata.GetValue(MetadataUtils.Kinds.KeyValues, ref slots);
             Assert.True(slots.Length == 3);
-            Assert.Equal(slots.Items().Select(x => x.Value.ToString()), new string[3] {"A","D","E"});
+            Assert.Equal(slots.Items().Select(x => x.Value.ToString()), new string[3] { "A", "D", "E" });
 
             column = result.Schema["CatH"];
-            Assert.Equal(column.Metadata.Schema.Select(x => x.Name), new string[1] { MetadataUtils.Kinds.KeyValues});
+            Assert.Equal(column.Metadata.Schema.Select(x => x.Name), new string[1] { MetadataUtils.Kinds.KeyValues });
             column.Metadata.GetValue(MetadataUtils.Kinds.KeyValues, ref slots);
             Assert.True(slots.Length == 2);
             Assert.Equal(slots.Items().Select(x => x.Value.ToString()), new string[2] { "D", "E" });