lib/matrix: Add hadamard_product/entrywise_product.

Based on a patch by Charley Hutchison. [GH-674]

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@60860 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

lib/matrix.rb

@@ -979,6 +979,17 @@ class Matrix
     end
   end
 
+  #
+  # Hadamard product
+  #    Matrix[[1,2], [3,4]].hadamard_product(Matrix[[1,2], [3,2]])
+  #      => 1  4
+  #         9  8
+  #
+  def hadamard_product(m)
+    combine(m){|a, b| a * b}
+  end
+  alias_method :entrywise_product, :hadamard_product
+
   #
   # Returns the inverse of the matrix.
   #   Matrix[[-1, -1], [0, -1]].inverse

test/matrix/test_matrix.rb

@@ -418,6 +418,20 @@ class TestMatrix < Test::Unit::TestCase
     assert_equal(Matrix[[1,1],[1,1]], Matrix[[2,2],[2,2]] / o)
   end
 
+  def test_hadamard_product
+    assert_equal(Matrix[[1,4], [9,16]], Matrix[[1,2], [3,4]].hadamard_product(Matrix[[1,2], [3,4]]))
+    assert_equal(Matrix[[2, 6, 12], [20, 30, 42]], @m1.hadamard_product(@n1))
+    o = Object.new
+    def o.to_matrix
+      Matrix[[1, 2, 3], [-1, 0, 1]]
+    end
+    assert_equal(Matrix[[1, 4, 9], [-4, 0, 6]], @m1.hadamard_product(o))
+    e = Matrix.empty(3, 0)
+    assert_equal(e, e.hadamard_product(e))
+    e = Matrix.empty(0, 3)
+    assert_equal(e, e.hadamard_product(e))
+  end
+
   def test_exp
     assert_equal(Matrix[[67,96],[48,99]], Matrix[[7,6],[3,9]] ** 2)
     assert_equal(Matrix.I(5), Matrix.I(5) ** -1)