Prefer feature_name over feature_names to match Python

lib/lightgbm/dataset.rb

@@ -2,7 +2,7 @@ module LightGBM
   class Dataset
     attr_reader :data, :params
 
-    def initialize(data, label: nil, weight: nil, group: nil, params: nil, reference: nil, used_indices: nil, categorical_feature: "auto", feature_names: nil)
+    def initialize(data, label: nil, weight: nil, group: nil, params: nil, reference: nil, used_indices: nil, categorical_feature: "auto", feature_name: nil, feature_names: nil)
       @data = data
       @label = label
       @weight = weight
@@ -11,7 +11,7 @@ def initialize(data, label: nil, weight: nil, group: nil, params: nil, reference
       @reference = reference
       @used_indices = used_indices
       @categorical_feature = categorical_feature
-      @feature_names = feature_names
+      @feature_name = feature_name || feature_names
 
       construct
     end
@@ -24,7 +24,7 @@ def weight
       field("weight")
     end
 
-    def feature_names
+    def feature_name
       # must preallocate space
       num_feature_names = ::FFI::MemoryPointer.new(:int)
       out_buffer_len = ::FFI::MemoryPointer.new(:size_t)
@@ -48,6 +48,7 @@ def feature_names
       # from most recent call (instead of num_features)
       str_ptrs[0, num_feature_names.read_int].map(&:read_string)
     end
+    alias_method :feature_names, :feature_name
 
     def label=(label)
       @label = label
@@ -64,12 +65,13 @@ def group=(group)
       set_field("group", group, type: :int32)
     end
 
-    def feature_names=(feature_names)
+    def feature_name=(feature_names)
       @feature_names = feature_names
       c_feature_names = ::FFI::MemoryPointer.new(:pointer, feature_names.size)
       c_feature_names.write_array_of_pointer(feature_names.map { |v| ::FFI::MemoryPointer.from_string(v) })
       check_result FFI.LGBM_DatasetSetFeatureNames(handle_pointer, c_feature_names, feature_names.size)
     end
+    alias_method :feature_names=, :feature_name=
 
     # TODO only update reference if not in chain
     def reference=(reference)
@@ -142,16 +144,16 @@ def construct
           ncol = data.column_count
           flat_data = data.to_a.flatten
         elsif daru?(data)
-          if @feature_names == "auto"
-            @feature_names = data.vectors.to_a
+          if @feature_name == "auto"
+            @feature_name = data.vectors.to_a
           end
           nrow, ncol = data.shape
           flat_data = data.map_rows(&:to_a).flatten
         elsif numo?(data)
           nrow, ncol = data.shape
         elsif rover?(data)
-          if @feature_names == "auto"
-            @feature_names = data.keys
+          if @feature_name == "auto"
+            @feature_name = data.keys
           end
           data = data.to_numo
           nrow, ncol = data.shape
@@ -176,7 +178,7 @@ def construct
       self.label = @label if @label
       self.weight = @weight if @weight
       self.group = @group if @group
-      self.feature_names = @feature_names if @feature_names
+      self.feature_name = @feature_name if @feature_name
     end
 
     def dump_text(filename)

test/dataset_test.rb

@@ -22,10 +22,10 @@ def test_weight
     assert weight, dataset.weight
   end
 
-  def test_feature_names
+  def test_feature_name
     data = [[1, 2], [3, 4]]
-    dataset = LightGBM::Dataset.new(data, feature_names: ["a", "b"])
-    assert_equal ["a", "b"], dataset.feature_names
+    dataset = LightGBM::Dataset.new(data, feature_name: ["a", "b"])
+    assert_equal ["a", "b"], dataset.feature_name
   end
 
   def test_num_data
@@ -61,9 +61,9 @@ def test_daru
     label = data["y"]
     data = data.delete_vector("y")
     dataset = LightGBM::Dataset.new(data, label: label)
-    assert_equal ["Column_0", "Column_1", "Column_2", "Column_3"], dataset.feature_names
+    assert_equal ["Column_0", "Column_1", "Column_2", "Column_3"], dataset.feature_name
 
-    dataset = LightGBM::Dataset.new(data, label: label, feature_names: "auto")
+    dataset = LightGBM::Dataset.new(data, label: label, feature_name: "auto")
     assert_equal ["x0", "x1", "x2", "x3"], dataset.feature_names
   end
 
@@ -74,7 +74,7 @@ def test_numo
     data = Numo::DFloat.new(3, 5).seq
     label = Numo::DFloat.new(3).seq
     dataset = LightGBM::Dataset.new(data, label: label)
-    assert_equal ["Column_0", "Column_1", "Column_2", "Column_3", "Column_4"], dataset.feature_names
+    assert_equal ["Column_0", "Column_1", "Column_2", "Column_3", "Column_4"], dataset.feature_name
   end
 
   def test_rover
@@ -84,10 +84,10 @@ def test_rover
     data = Rover.read_csv(data_path)
     label = data.delete("y")
     dataset = LightGBM::Dataset.new(data, label: label)
-    assert_equal ["Column_0", "Column_1", "Column_2", "Column_3"], dataset.feature_names
+    assert_equal ["Column_0", "Column_1", "Column_2", "Column_3"], dataset.feature_name
 
-    dataset = LightGBM::Dataset.new(data, label: label, feature_names: "auto")
-    assert_equal ["x0", "x1", "x2", "x3"], dataset.feature_names
+    dataset = LightGBM::Dataset.new(data, label: label, feature_name: "auto")
+    assert_equal ["x0", "x1", "x2", "x3"], dataset.feature_name
   end
 
   def test_copy