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* lib/matrix.rb: Add Matrix#laplace_expansion.

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patch by gogo tanaka [#10073]

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@47835 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
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marcandre 2014-10-07 19:30:48 +00:00
parent 19a1257d6c
commit 56d5728589
4 changed files with 58 additions and 0 deletions
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5
ChangeLog
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@ -1,3 +1,8 @@
Wed Oct 8 04:30:29 2014 Marc-Andre Lafortune <ruby-core@marc-andre.ca>
* lib/matrix.rb: Add Matrix#laplace_expansion.
patch by gogo tanaka [#10073]
Wed Oct 8 04:29:21 2014 Marc-Andre Lafortune <ruby-core@marc-andre.ca>
* lib/matrix.rb: Add Vector.basis.

2
NEWS
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@ -84,6 +84,8 @@ with all sufficient information, see the ChangeLog file.
which is obtained by multiplying the first minor by (-1)**(row + column).
* 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
along the +num+ -th row or column.
* Vector.basis(size:, index:) returns the specified basis vector
* Method

33
lib/matrix.rb
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@ -62,6 +62,8 @@ end
# * #minor(*param)
# * #first_minor(row, column)
# * #cofactor(row, column)
# * #laplace_expansion(row_or_column: num)
# * #cofactor_expansion(row_or_column: num)
#
# Properties of a matrix:
# * #diagonal?
@ -685,6 +687,37 @@ class Matrix
det_of_minor * (-1) ** (row + column)
end
#
# Returns the Laplace expansion along given row or column.
#
# Matrix[[7,6], [3,9]].laplace_expansion(column: 1)
# => 45
#
# Matrix[[Vector[1, 0], Vector[0, 1]], [2, 3]].laplace_expansion(row: 0)
# => Vector[3, -2]
#
#
def laplace_expansion(row: nil, column: nil)
num = row || column
if !num || (row && column)
raise ArgumentError, "exactly one the row or column arguments must be specified"
end
Matrix.Raise ErrDimensionMismatch unless square?
raise RuntimeError, "laplace_expansion of empty matrix is not defined" if empty?
unless 0 <= num && num < row_count
raise ArgumentError, "invalid num (#{num.inspect} for 0..#{row_count - 1})"
end
send(row ? :row : :column, num).map.with_index { |e, k|
e * cofactor(*(row ? [num, k] : [k,num]))
}.inject(:+)
end
alias_method :cofactor_expansion, :laplace_expansion
#--
# TESTING -=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
#++

18
test/matrix/test_matrix.rb
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@ -293,6 +293,24 @@ class TestMatrix < Test::Unit::TestCase
assert_raise(ExceptionForMatrix::ErrDimensionMismatch) { Matrix[[2,0,1],[0,-2,2]].cofactor(0, 0) }
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))
assert_equal(0, Matrix[[0,0],[0,0]].laplace_expansion(column: 0))
assert_equal(-7, Matrix[[0,0,1],[0,7,6],[1,3,9]].laplace_expansion(column: 2))
assert_equal(Vector[3, -2], Matrix[[Vector[1, 0], Vector[0, 1]], [2, 3]].laplace_expansion(row: 0))
assert_raise(ExceptionForMatrix::ErrDimensionMismatch) { @m1.laplace_expansion(row: 1) }
assert_raise(ArgumentError) { Matrix[[7,6], [3,9]].laplace_expansion() }
assert_raise(ArgumentError) { Matrix[[7,6], [3,9]].laplace_expansion(foo: 1) }
assert_raise(ArgumentError) { Matrix[[7,6], [3,9]].laplace_expansion(row: 1, column: 1) }
assert_raise(ArgumentError) { Matrix[[7,6], [3,9]].laplace_expansion(row: 2) }
assert_raise(ArgumentError) { Matrix[[0,0,1],[0,7,6],[1,3,9]].laplace_expansion(column: -1) }
assert_raise(RuntimeError) { Matrix.empty(0, 0).laplace_expansion(row: 0) }
end
def test_regular?
assert(Matrix[[1, 0], [0, 1]].regular?)
assert(Matrix[[1, 0, 0], [0, 1, 0], [0, 0, 1]].regular?)