Add abs to Matrix (#2199)

lib/matrix.rb

@@ -1225,6 +1225,13 @@ class Matrix
     collect {|e| -e }
   end
 
+  #
+  # Returns the absolute value elementwise
+  #
+  def abs
+    collect(&:abs)
+  end
+
   #--
   # MATRIX FUNCTIONS -=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
   #++

test/matrix/test_matrix.rb

@@ -583,6 +583,11 @@ class TestMatrix < Test::Unit::TestCase
     assert_equal(1, s1 ** o)
   end
 
+  def test_abs
+    s1 = @a3.abs
+    assert_equal(s1, Matrix[[4, 1, 3], [0, 3, 7], [11, 4, 2]])
+  end
+
   def test_hstack
     assert_equal Matrix[[1,2,3,2,3,4,1,2,3], [4,5,6,5,6,7,4,5,6]],
       @m1.hstack(@n1, @m1)