Added to_numo method to Series

CHANGELOG.md

@@ -1,3 +1,7 @@
+## 0.3.1 (unreleased)
+
+- Added `to_numo` method to `Series`
+
 ## 0.3.0 (2023-02-15)
 
 - Updated Polars to 0.27.1

Gemfile

@@ -7,6 +7,7 @@ gem "rake-compiler"
 gem "minitest"
 gem "activerecord"
 gem "sqlite3"
+gem "numo-narray"
 
 # https://github.com/lsegal/yard/issues/1321
 gem "yard", require: false

lib/polars/series.rb

@@ -1823,8 +1823,35 @@ def is_utf8
     # def view
     # end
 
-    # def to_numo
-    # end
+    # Convert this Series to a Numo array. This operation clones data but is completely safe.
+    #
+    # @return [Numo::NArray]
+    #
+    # @example
+    #   s = Polars::Series.new("a", [1, 2, 3])
+    #   s.to_numo
+    #   # =>
+    #   # Numo::Int64#shape=[3]
+    #   # [1, 2, 3]
+    def to_numo
+      if !has_validity && is_numeric
+        # TODO make more efficient
+        {
+          UInt8 => Numo::UInt8,
+          UInt16 => Numo::UInt16,
+          UInt32 => Numo::UInt32,
+          UInt64 => Numo::UInt64,
+          Int8 => Numo::Int8,
+          Int16 => Numo::Int16,
+          Int32 => Numo::Int32,
+          Int64 => Numo::Int64,
+          Float32 => Numo::SFloat,
+          Float64 => Numo::DFloat
+        }.fetch(dtype).cast(to_a)
+      else
+        raise Todo
+      end
+    end
 
     # Set masked values.
     #

test/numo_test.rb

@@ -0,0 +1,15 @@
+require_relative "test_helper"
+
+class NumoTest < Minitest::Test
+  def test_series_int
+    s = Polars::Series.new([1, 2, 3])
+    assert_kind_of Numo::Int64, s.to_numo
+    assert_equal s.to_a, s.to_numo.to_a
+  end
+
+  def test_series_float
+    s = Polars::Series.new([1.5, 2.5, 3.5])
+    assert_kind_of Numo::Float64, s.to_numo
+    assert_equal s.to_a, s.to_numo.to_a
+  end
+end