Added support for hashes to Dataset

Author: ankane

CHANGELOG.md

@@ -1,6 +1,7 @@
 ## 0.4.0 (unreleased)
 
 - Added support for hashes and Rover data frames to `predict` method
+- Added support for hashes to `Dataset`
 - Changed `Dataset` to use column names for feature names with Rover and Daru
 - Changed `predict` method to match feature names with Daru
 - Dropped support for Ruby < 3.1

lib/lightgbm/dataset.rb

@@ -66,6 +66,7 @@ def group=(group)
     end
 
     def feature_name=(feature_names)
+      feature_names = feature_names.map(&:to_s)
       @feature_names = feature_names
       c_feature_names = ::FFI::MemoryPointer.new(:pointer, feature_names.size)
       # keep reference to string pointers
@@ -154,6 +155,14 @@ def construct
           end
           data = data.to_numo
           nrow, ncol = data.shape
+        elsif data.is_a?(Array) && data.first.is_a?(Hash)
+          keys = data.first.keys
+          if @feature_name == "auto"
+            @feature_name = keys
+          end
+          nrow = data.count
+          ncol = data.first.count
+          flat_data = data.flat_map { |v| v.fetch_values(*keys) }
         else
           nrow = data.count
           ncol = data.first.count

test/dataset_test.rb

@@ -50,6 +50,22 @@ def test_dump_text
     assert File.exist?(tempfile)
   end
 
+  def test_hashes_string_keys
+    data = [{"x0" => 1, "x1" => 2}, {"x0" => 3, "x1" => 4}, {"x0" => 5, "x1" => 6}]
+    dataset = LightGBM::Dataset.new(data)
+    assert_equal 3, dataset.num_data
+    assert_equal 2, dataset.num_feature
+    assert_equal ["x0", "x1"], dataset.feature_name
+  end
+
+  def test_hashes_symbol_keys
+    data = [{x0: 1, x1: 2}, {x0: 3, x1: 4}, {x0: 5, x1: 6}]
+    dataset = LightGBM::Dataset.new(data)
+    assert_equal 3, dataset.num_data
+    assert_equal 2, dataset.num_feature
+    assert_equal ["x0", "x1"], dataset.feature_name
+  end
+
   def test_matrix
     data = Matrix.build(3, 3) { |row, col| row + col }
     label = Vector.elements([4, 5, 6])