* lib/matrix.rb: Add Matrix#adjucate

patch by gogo tanaka [#10056]

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@48182 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

ChangeLog

@@ -1,3 +1,8 @@
+Wed Oct 29 11:43:11 2014  Marc-Andre Lafortune  <ruby-core@marc-andre.ca>
+
+	* lib/matrix.rb: Add Matrix#adjucate
+	  patch by gogo tanaka [#10056]
+
 Wed Oct 29 11:42:33 2014  Marc-Andre Lafortune  <ruby-core@marc-andre.ca>
 
 	* lib/matrix.rb: Add aliases for Vector#cross & dot

NEWS

@@ -148,6 +148,7 @@ with all sufficient information, see the ChangeLog file.
       by deleting the specified row and column.
     * Matrix#cofactor(row, column) returns the (row, column) cofactor
       which is obtained by multiplying the first minor by (-1)**(row + column).
+    * Matrix#adjugate returns the adjugate of the matrix.
     * hstack and vstack are new instance and class methods to stack matrices
       horizontally and vertically.
     * Matrix#laplace_expansion(row_or_column: num) returns the laplace_expansion

lib/matrix.rb

@@ -62,6 +62,7 @@ end
 # * #minor(*param)
 # * #first_minor(row, column)
 # * #cofactor(row, column)
+# * #adjugate
 # * #laplace_expansion(row_or_column: num)
 # * #cofactor_expansion(row_or_column: num)
 #
@@ -689,6 +690,20 @@ class Matrix
     det_of_minor * (-1) ** (row + column)
   end
 
+  #
+  # Returns the adjugate of the matrix.
+  #
+  #   Matrix[ [7,6],[3,9] ].adjugate
+  #     => 9 -6
+  #        -3 7
+  #
+  def adjugate
+    Matrix.Raise ErrDimensionMismatch unless square?
+    Matrix.build(row_count, column_count) do |row, column|
+      cofactor(column, row)
+    end
+  end
+
   #
   # Returns the Laplace expansion along given row or column.
   #

test/matrix/test_matrix.rb

@@ -14,6 +14,9 @@ class TestMatrix < Test::Unit::TestCase
     @c1 = Matrix[[Complex(1,2), Complex(0,1), 0], [1, 2, 3]]
     @e1 = Matrix.empty(2,0)
     @e2 = Matrix.empty(0,3)
+    @a3  = Matrix[[4, 1, -3], [0, 3, 7], [11, -4, 2]]
+    @a5  = Matrix[[2, 0, 9, 3, 9], [8, 7, 0, 1, 9], [7, 5, 6, 6, 5], [0, 7, 8, 3, 0], [7, 8, 2, 3, 1]]
+    @b3  = Matrix[[-7, 7, -10], [9, -3, -2], [-1, 3, 9]]
   end
 
   def test_matrix
@@ -302,6 +305,18 @@ class TestMatrix < Test::Unit::TestCase
     assert_raise(ExceptionForMatrix::ErrDimensionMismatch) { Matrix[[2,0,1],[0,-2,2]].cofactor(0, 0) }
   end
 
+  def test_adjugate
+    assert_equal(Matrix.empty, Matrix.empty.adjugate)
+    assert_equal(Matrix[[1]], Matrix[[5]].adjugate)
+    assert_equal(Matrix[[9,-6],[-3,7]], Matrix[[7,6],[3,9]].adjugate)
+    assert_equal(Matrix[[45,3,-7],[6,-1,0],[-7,0,0]], Matrix[[0,0,1],[0,7,6],[1,3,9]].adjugate)
+    assert_equal(Matrix.identity(5), (@a5.adjugate * @a5) / @a5.det)
+    assert_equal(Matrix.I(3), Matrix.I(3).adjugate)
+    assert_equal((@a3 * @b3).adjugate, @b3.adjugate * @a3.adjugate)
+    assert_equal(4**(@a3.row_count-1) * @a3.adjugate, (4 * @a3).adjugate)
+    assert_raise(ExceptionForMatrix::ErrDimensionMismatch) { @m1.adjugate }
+  end
+
   def test_laplace_expansion
     assert_equal(1, Matrix[[1]].laplace_expansion(row: 0))
     assert_equal(45, Matrix[[7,6], [3,9]].laplace_expansion(row: 1))