class Matrix

The Matrix class represents a mathematical matrix. It provides methods for creating matrices, operating on them arithmetically and algebraically, and determining their mathematical properties such as trace, rank, inverse, determinant, or eigensystem.

Constants

SELECTORS

Attributes

column_count[R]

Returns the number of columns.

column_size[R]

Returns the number of columns.

rows[R]

instance creations

Public Class Methods

I(n)
Alias for: identity
[](*rows) click to toggle source

Creates a matrix where each argument is a row.

Matrix[ [25, 93], [-1, 66] ]
   =>  25 93
       -1 66
# File lib/matrix.rb, line 49
def Matrix.[](*rows)
  rows(rows, false)
end
build(row_count, column_count = row_count) { |i, j| ... } click to toggle source

Creates a matrix of size row_count x column_count. It fills the values by calling the given block, passing the current row and column. Returns an enumerator if no block is given.

m = Matrix.build(2, 4) {|row, col| col - row }
  => Matrix[[0, 1, 2, 3], [-1, 0, 1, 2]]
m = Matrix.build(3) { rand }
  => a 3x3 matrix with random elements
# File lib/matrix.rb, line 94
def Matrix.build(row_count, column_count = row_count)
  row_count = CoercionHelper.coerce_to_int(row_count)
  column_count = CoercionHelper.coerce_to_int(column_count)
  raise ArgumentError if row_count < 0 || column_count < 0
  return to_enum :build, row_count, column_count unless block_given?
  rows = Array.new(row_count) do |i|
    Array.new(column_count) do |j|
      yield i, j
    end
  end
  new rows, column_count
end
column_vector(column) click to toggle source

Creates a single-column matrix where the values of that column are as given in column.

Matrix.column_vector([4,5,6])
  => 4
     5
     6
# File lib/matrix.rb, line 180
def Matrix.column_vector(column)
  column = convert_to_array(column)
  new [column].transpose, 1
end
columns(columns) click to toggle source

Creates a matrix using columns as an array of column vectors.

Matrix.columns([[25, 93], [-1, 66]])
   =>  25 -1
       93 66
# File lib/matrix.rb, line 79
def Matrix.columns(columns)
  rows(columns, false).transpose
end
combine(*matrices) { |map{|m| m}| ... } click to toggle source

Create a matrix by combining matrices entrywise, using the given block

x = Matrix[[6, 6], [4, 4]]
y = Matrix[[1, 2], [3, 4]]
Matrix.combine(x, y) {|a, b| a - b} # => Matrix[[5, 4], [1, 0]]
# File lib/matrix.rb, line 257
def Matrix.combine(*matrices)
  return to_enum(__method__, *matrices) unless block_given?

  return Matrix.empty if matrices.empty?
  matrices.map!(&CoercionHelper.method(:coerce_to_matrix))
  x = matrices.first
  matrices.each do |m|
    Matrix.Raise ErrDimensionMismatch unless x.row_count == m.row_count && x.column_count == m.column_count
  end

  rows = Array.new(x.row_count) do |i|
    Array.new(x.column_count) do |j|
      yield matrices.map{|m| m[i,j]}
    end
  end
  new rows, x.column_count
end
diagonal(*values) click to toggle source

Creates a matrix where the diagonal elements are composed of values.

Matrix.diagonal(9, 5, -3)
  =>  9  0  0
      0  5  0
      0  0 -3
# File lib/matrix.rb, line 114
def Matrix.diagonal(*values)
  size = values.size
  return Matrix.empty if size == 0
  rows = Array.new(size) {|j|
    row = Array.new(size, 0)
    row[j] = values[j]
    row
  }
  new rows
end
empty(row_count = 0, column_count = 0) click to toggle source

Creates a empty matrix of row_count x column_count. At least one of row_count or column_count must be 0.

m = Matrix.empty(2, 0)
m == Matrix[ [], [] ]
  => true
n = Matrix.empty(0, 3)
n == Matrix.columns([ [], [], [] ])
  => true
m * n
  => Matrix[[0, 0, 0], [0, 0, 0]]
# File lib/matrix.rb, line 198
def Matrix.empty(row_count = 0, column_count = 0)
  raise ArgumentError, "One size must be 0" if column_count != 0 && row_count != 0
  raise ArgumentError, "Negative size" if column_count < 0 || row_count < 0

  new([[]]*row_count, column_count)
end
hstack(x, *matrices) click to toggle source

Create a matrix by stacking matrices horizontally

x = Matrix[[1, 2], [3, 4]]
y = Matrix[[5, 6], [7, 8]]
Matrix.hstack(x, y) # => Matrix[[1, 2, 5, 6], [3, 4, 7, 8]]
# File lib/matrix.rb, line 233
def Matrix.hstack(x, *matrices)
  x = CoercionHelper.coerce_to_matrix(x)
  result = x.send(:rows).map(&:dup)
  total_column_count = x.column_count
  matrices.each do |m|
    m = CoercionHelper.coerce_to_matrix(m)
    if m.row_count != x.row_count
      raise ErrDimensionMismatch, "The given matrices must have #{x.row_count} rows, but one has #{m.row_count}"
    end
    result.each_with_index do |row, i|
      row.concat m.send(:rows)[i]
    end
    total_column_count += m.column_count
  end
  new result, total_column_count
end
identity(n) click to toggle source

Creates an n by n identity matrix.

Matrix.identity(2)
  => 1 0
     0 1
# File lib/matrix.rb, line 142
def Matrix.identity(n)
  scalar(n, 1)
end
Also aliased as: unit, I
new(rows, column_count = rows[0].size) click to toggle source

::new is private; use ::rows, columns, [], etc… to create.

# File lib/matrix.rb, line 282
def initialize(rows, column_count = rows[0].size)
  # No checking is done at this point. rows must be an Array of Arrays.
  # column_count must be the size of the first row, if there is one,
  # otherwise it *must* be specified and can be any integer >= 0
  @rows = rows
  @column_count = column_count
end
row_vector(row) click to toggle source

Creates a single-row matrix where the values of that row are as given in row.

Matrix.row_vector([4,5,6])
  => 4 5 6
# File lib/matrix.rb, line 167
def Matrix.row_vector(row)
  row = convert_to_array(row)
  new [row]
end
rows(rows, copy = true) click to toggle source

Creates a matrix where rows is an array of arrays, each of which is a row of the matrix. If the optional argument copy is false, use the given arrays as the internal structure of the matrix without copying.

Matrix.rows([[25, 93], [-1, 66]])
   =>  25 93
       -1 66
# File lib/matrix.rb, line 61
def Matrix.rows(rows, copy = true)
  rows = convert_to_array(rows, copy)
  rows.map! do |row|
    convert_to_array(row, copy)
  end
  size = (rows[0] || []).size
  rows.each do |row|
    raise ErrDimensionMismatch, "row size differs (#{row.size} should be #{size})" unless row.size == size
  end
  new rows, size
end
scalar(n, value) click to toggle source

Creates an n by n diagonal matrix where each diagonal element is value.

Matrix.scalar(2, 5)
  => 5 0
     0 5
# File lib/matrix.rb, line 132
def Matrix.scalar(n, value)
  diagonal(*Array.new(n, value))
end
unit(n)
Alias for: identity
vstack(x, *matrices) click to toggle source

Create a matrix by stacking matrices vertically

x = Matrix[[1, 2], [3, 4]]
y = Matrix[[5, 6], [7, 8]]
Matrix.vstack(x, y) # => Matrix[[1, 2], [3, 4], [5, 6], [7, 8]]
# File lib/matrix.rb, line 212
def Matrix.vstack(x, *matrices)
  x = CoercionHelper.coerce_to_matrix(x)
  result = x.send(:rows).map(&:dup)
  matrices.each do |m|
    m = CoercionHelper.coerce_to_matrix(m)
    if m.column_count != x.column_count
      raise ErrDimensionMismatch, "The given matrices must have #{x.column_count} columns, but one has #{m.column_count}"
    end
    result.concat(m.send(:rows))
  end
  new result, x.column_count
end
zero(row_count, column_count = row_count) click to toggle source

Creates a zero matrix.

Matrix.zero(2)
  => 0 0
     0 0
# File lib/matrix.rb, line 156
def Matrix.zero(row_count, column_count = row_count)
  rows = Array.new(row_count){Array.new(column_count, 0)}
  new rows, column_count
end

Public Instance Methods

*(m) click to toggle source

Matrix multiplication.

Matrix[[2,4], [6,8]] * Matrix.identity(2)
  => 2 4
     6 8
# File lib/matrix.rb, line 879
def *(m) # m is matrix or vector or number
  case(m)
  when Numeric
    rows = @rows.collect {|row|
      row.collect {|e| e * m }
    }
    return new_matrix rows, column_count
  when Vector
    m = self.class.column_vector(m)
    r = self * m
    return r.column(0)
  when Matrix
    Matrix.Raise ErrDimensionMismatch if column_count != m.row_count

    rows = Array.new(row_count) {|i|
      Array.new(m.column_count) {|j|
        (0 ... column_count).inject(0) do |vij, k|
          vij + self[i, k] * m[k, j]
        end
      }
    }
    return new_matrix rows, m.column_count
  else
    return apply_through_coercion(m, __method__)
  end
end
**(other) click to toggle source

Matrix exponentiation. Equivalent to multiplying the matrix by itself N times. Non integer exponents will be handled by diagonalizing the matrix.

Matrix[[7,6], [3,9]] ** 2
  => 67 96
     48 99
# File lib/matrix.rb, line 1057
def **(other)
  case other
  when Integer
    x = self
    if other <= 0
      x = self.inverse
      return self.class.identity(self.column_count) if other == 0
      other = -other
    end
    z = nil
    loop do
      z = z ? z * x : x if other[0] == 1
      return z if (other >>= 1).zero?
      x *= x
    end
  when Numeric
    v, d, v_inv = eigensystem
    v * self.class.diagonal(*d.each(:diagonal).map{|e| e ** other}) * v_inv
  else
    Matrix.Raise ErrOperationNotDefined, "**", self.class, other.class
  end
end
+(m) click to toggle source

Matrix addition.

Matrix.scalar(2,5) + Matrix[[1,0], [-4,7]]
  =>  6  0
     -4 12
# File lib/matrix.rb, line 912
def +(m)
  case m
  when Numeric
    Matrix.Raise ErrOperationNotDefined, "+", self.class, m.class
  when Vector
    m = self.class.column_vector(m)
  when Matrix
  else
    return apply_through_coercion(m, __method__)
  end

  Matrix.Raise ErrDimensionMismatch unless row_count == m.row_count && column_count == m.column_count

  rows = Array.new(row_count) {|i|
    Array.new(column_count) {|j|
      self[i, j] + m[i, j]
    }
  }
  new_matrix rows, column_count
end
+@() click to toggle source
# File lib/matrix.rb, line 1080
def +@
  self
end
-(m) click to toggle source

Matrix subtraction.

Matrix[[1,5], [4,2]] - Matrix[[9,3], [-4,1]]
  => -8  2
      8  1
# File lib/matrix.rb, line 939
def -(m)
  case m
  when Numeric
    Matrix.Raise ErrOperationNotDefined, "-", self.class, m.class
  when Vector
    m = self.class.column_vector(m)
  when Matrix
  else
    return apply_through_coercion(m, __method__)
  end

  Matrix.Raise ErrDimensionMismatch unless row_count == m.row_count && column_count == m.column_count

  rows = Array.new(row_count) {|i|
    Array.new(column_count) {|j|
      self[i, j] - m[i, j]
    }
  }
  new_matrix rows, column_count
end
-@() click to toggle source
# File lib/matrix.rb, line 1084
def -@
  collect {|e| -e }
end
/(other) click to toggle source

Matrix division (multiplication by the inverse).

Matrix[[7,6], [3,9]] / Matrix[[2,9], [3,1]]
  => -7  1
     -3 -6
# File lib/matrix.rb, line 966
def /(other)
  case other
  when Numeric
    rows = @rows.collect {|row|
      row.collect {|e| e / other }
    }
    return new_matrix rows, column_count
  when Matrix
    return self * other.inverse
  else
    return apply_through_coercion(other, __method__)
  end
end
==(other) click to toggle source

Returns true if and only if the two matrices contain equal elements.

# File lib/matrix.rb, line 841
def ==(other)
  return false unless Matrix === other &&
                      column_count == other.column_count # necessary for empty matrices
  rows == other.rows
end
[](i, j) click to toggle source

Returns element (i,j) of the matrix. That is: row i, column j.

# File lib/matrix.rb, line 298
def [](i, j)
  @rows.fetch(i){return nil}[j]
end
Also aliased as: element, component
adjugate() click to toggle source

Returns the adjugate of the matrix.

Matrix[ [7,6],[3,9] ].adjugate
  => 9 -6
     -3 7
# File lib/matrix.rb, line 627
def adjugate
  Matrix.Raise ErrDimensionMismatch unless square?
  Matrix.build(row_count, column_count) do |row, column|
    cofactor(column, row)
  end
end
clone() click to toggle source

Returns a clone of the matrix, so that the contents of each do not reference identical objects. There should be no good reason to do this since Matrices are immutable.

# File lib/matrix.rb, line 858
def clone
  new_matrix @rows.map(&:dup), column_count
end
coerce(other) click to toggle source

The coerce method provides support for Ruby type coercion. This coercion mechanism is used by Ruby to handle mixed-type numeric operations: it is intended to find a compatible common type between the two operands of the operator. See also Numeric#coerce.

# File lib/matrix.rb, line 1394
def coerce(other)
  case other
  when Numeric
    return Scalar.new(other), self
  else
    raise TypeError, "#{self.class} can't be coerced into #{other.class}"
  end
end
cofactor(row, column) click to toggle source

Returns the (row, column) cofactor which is obtained by multiplying the first minor by (-1)**(row + column).

Matrix.diagonal(9, 5, -3, 4).cofactor(1, 1)
  => -108
# File lib/matrix.rb, line 612
def cofactor(row, column)
  raise RuntimeError, "cofactor of empty matrix is not defined" if empty?
  Matrix.Raise ErrDimensionMismatch unless square?

  det_of_minor = first_minor(row, column).determinant
  det_of_minor * (-1) ** (row + column)
end
cofactor_expansion(row: nil, column: nil)
Alias for: laplace_expansion
collect() { |e| ... } click to toggle source

Returns a matrix that is the result of iteration of the given block over all elements of the matrix.

Matrix[ [1,2], [3,4] ].collect { |e| e**2 }
  => 1  4
     9 16
# File lib/matrix.rb, line 366
def collect(&block) # :yield: e
  return to_enum(:collect) unless block_given?
  rows = @rows.collect{|row| row.collect(&block)}
  new_matrix rows, column_count
end
Also aliased as: map
column(j) { |e| ... } click to toggle source

Returns column vector number j of the matrix as a Vector (starting at 0 like an array). When a block is given, the elements of that vector are iterated.

# File lib/matrix.rb, line 343
def column(j) # :yield: e
  if block_given?
    return self if j >= column_count || j < -column_count
    row_count.times do |i|
      yield @rows[i][j]
    end
    self
  else
    return nil if j >= column_count || j < -column_count
    col = Array.new(row_count) {|i|
      @rows[i][j]
    }
    Vector.elements(col, false)
  end
end
column_vectors() click to toggle source

Returns an array of the column vectors of the matrix. See Vector.

# File lib/matrix.rb, line 1415
def column_vectors
  Array.new(column_count) {|i|
    column(i)
  }
end
combine(*matrices, &block) click to toggle source
# File lib/matrix.rb, line 275
def combine(*matrices, &block)
  Matrix.combine(self, *matrices, &block)
end
component(i, j)
Alias for: []
conj()
Alias for: conjugate
conjugate() click to toggle source

Returns the conjugate of the matrix.

Matrix[[Complex(1,2), Complex(0,1), 0], [1, 2, 3]]
  => 1+2i   i  0
        1   2  3
Matrix[[Complex(1,2), Complex(0,1), 0], [1, 2, 3]].conjugate
  => 1-2i  -i  0
        1   2  3
# File lib/matrix.rb, line 1340
def conjugate
  collect(&:conjugate)
end
Also aliased as: conj
det()
Alias for: determinant
det_e()
Alias for: determinant_e
determinant() click to toggle source

Returns the determinant of the matrix.

Beware that using Float values can yield erroneous results because of their lack of precision. Consider using exact types like Rational or BigDecimal instead.

Matrix[[7,6], [3,9]].determinant
  => 45
# File lib/matrix.rb, line 1102
def determinant
  Matrix.Raise ErrDimensionMismatch unless square?
  m = @rows
  case row_count
    # Up to 4x4, give result using Laplacian expansion by minors.
    # This will typically be faster, as well as giving good results
    # in case of Floats
  when 0
    +1
  when 1
    + m[0][0]
  when 2
    + m[0][0] * m[1][1] - m[0][1] * m[1][0]
  when 3
    m0, m1, m2 = m
    + m0[0] * m1[1] * m2[2] - m0[0] * m1[2] * m2[1] \
    - m0[1] * m1[0] * m2[2] + m0[1] * m1[2] * m2[0] \
    + m0[2] * m1[0] * m2[1] - m0[2] * m1[1] * m2[0]
  when 4
    m0, m1, m2, m3 = m
    + m0[0] * m1[1] * m2[2] * m3[3] - m0[0] * m1[1] * m2[3] * m3[2] \
    - m0[0] * m1[2] * m2[1] * m3[3] + m0[0] * m1[2] * m2[3] * m3[1] \
    + m0[0] * m1[3] * m2[1] * m3[2] - m0[0] * m1[3] * m2[2] * m3[1] \
    - m0[1] * m1[0] * m2[2] * m3[3] + m0[1] * m1[0] * m2[3] * m3[2] \
    + m0[1] * m1[2] * m2[0] * m3[3] - m0[1] * m1[2] * m2[3] * m3[0] \
    - m0[1] * m1[3] * m2[0] * m3[2] + m0[1] * m1[3] * m2[2] * m3[0] \
    + m0[2] * m1[0] * m2[1] * m3[3] - m0[2] * m1[0] * m2[3] * m3[1] \
    - m0[2] * m1[1] * m2[0] * m3[3] + m0[2] * m1[1] * m2[3] * m3[0] \
    + m0[2] * m1[3] * m2[0] * m3[1] - m0[2] * m1[3] * m2[1] * m3[0] \
    - m0[3] * m1[0] * m2[1] * m3[2] + m0[3] * m1[0] * m2[2] * m3[1] \
    + m0[3] * m1[1] * m2[0] * m3[2] - m0[3] * m1[1] * m2[2] * m3[0] \
    - m0[3] * m1[2] * m2[0] * m3[1] + m0[3] * m1[2] * m2[1] * m3[0]
  else
    # For bigger matrices, use an efficient and general algorithm.
    # Currently, we use the Gauss-Bareiss algorithm
    determinant_bareiss
  end
end
Also aliased as: det
determinant_e() click to toggle source

deprecated; use #determinant

# File lib/matrix.rb, line 1184
def determinant_e
  warn "Matrix#determinant_e is deprecated; use #determinant", uplevel: 1
  determinant
end
Also aliased as: det_e
diagonal?() click to toggle source

Returns true if this is a diagonal matrix. Raises an error if matrix is not square.

# File lib/matrix.rb, line 673
def diagonal?
  Matrix.Raise ErrDimensionMismatch unless square?
  each(:off_diagonal).all?(&:zero?)
end
each(which = :all) { |e| ... } click to toggle source

Yields all elements of the matrix, starting with those of the first row, or returns an Enumerator if no block given. Elements can be restricted by passing an argument:

  • :all (default): yields all elements

  • :diagonal: yields only elements on the diagonal

  • :off_diagonal: yields all elements except on the diagonal

  • :lower: yields only elements on or below the diagonal

  • :strict_lower: yields only elements below the diagonal

  • :strict_upper: yields only elements above the diagonal

  • :upper: yields only elements on or above the diagonal

    Matrix[ [1,2], [3,4] ].each { |e| puts e }

    # => prints the numbers 1 to 4
    

    Matrix[ [1,2], [3,4] ].each(:strict_lower).to_a # => [3]

# File lib/matrix.rb, line 389
def each(which = :all) # :yield: e
  return to_enum :each, which unless block_given?
  last = column_count - 1
  case which
  when :all
    block = Proc.new
    @rows.each do |row|
      row.each(&block)
    end
  when :diagonal
    @rows.each_with_index do |row, row_index|
      yield row.fetch(row_index){return self}
    end
  when :off_diagonal
    @rows.each_with_index do |row, row_index|
      column_count.times do |col_index|
        yield row[col_index] unless row_index == col_index
      end
    end
  when :lower
    @rows.each_with_index do |row, row_index|
      0.upto([row_index, last].min) do |col_index|
        yield row[col_index]
      end
    end
  when :strict_lower
    @rows.each_with_index do |row, row_index|
      [row_index, column_count].min.times do |col_index|
        yield row[col_index]
      end
    end
  when :strict_upper
    @rows.each_with_index do |row, row_index|
      (row_index+1).upto(last) do |col_index|
        yield row[col_index]
      end
    end
  when :upper
    @rows.each_with_index do |row, row_index|
      row_index.upto(last) do |col_index|
        yield row[col_index]
      end
    end
  else
    raise ArgumentError, "expected #{which.inspect} to be one of :all, :diagonal, :off_diagonal, :lower, :strict_lower, :strict_upper or :upper"
  end
  self
end
each_with_index(which = :all) { |e, row, column| ... } click to toggle source

Same as each, but the row index and column index in addition to the element

Matrix[ [1,2], [3,4] ].each_with_index do |e, row, col|
  puts "#{e} at #{row}, #{col}"
end
  # => Prints:
  #    1 at 0, 0
  #    2 at 0, 1
  #    3 at 1, 0
  #    4 at 1, 1
# File lib/matrix.rb, line 450
def each_with_index(which = :all) # :yield: e, row, column
  return to_enum :each_with_index, which unless block_given?
  last = column_count - 1
  case which
  when :all
    @rows.each_with_index do |row, row_index|
      row.each_with_index do |e, col_index|
        yield e, row_index, col_index
      end
    end
  when :diagonal
    @rows.each_with_index do |row, row_index|
      yield row.fetch(row_index){return self}, row_index, row_index
    end
  when :off_diagonal
    @rows.each_with_index do |row, row_index|
      column_count.times do |col_index|
        yield row[col_index], row_index, col_index unless row_index == col_index
      end
    end
  when :lower
    @rows.each_with_index do |row, row_index|
      0.upto([row_index, last].min) do |col_index|
        yield row[col_index], row_index, col_index
      end
    end
  when :strict_lower
    @rows.each_with_index do |row, row_index|
      [row_index, column_count].min.times do |col_index|
        yield row[col_index], row_index, col_index
      end
    end
  when :strict_upper
    @rows.each_with_index do |row, row_index|
      (row_index+1).upto(last) do |col_index|
        yield row[col_index], row_index, col_index
      end
    end
  when :upper
    @rows.each_with_index do |row, row_index|
      row_index.upto(last) do |col_index|
        yield row[col_index], row_index, col_index
      end
    end
  else
    raise ArgumentError, "expected #{which.inspect} to be one of :all, :diagonal, :off_diagonal, :lower, :strict_lower, :strict_upper or :upper"
  end
  self
end
eigen()
Alias for: eigensystem
eigensystem() click to toggle source

Returns the Eigensystem of the matrix; see EigenvalueDecomposition.

m = Matrix[[1, 2], [3, 4]]
v, d, v_inv = m.eigensystem
d.diagonal? # => true
v.inv == v_inv # => true
(v * d * v_inv).round(5) == m # => true
# File lib/matrix.rb, line 1307
def eigensystem
  EigenvalueDecomposition.new(self)
end
Also aliased as: eigen
element(i, j)
Alias for: []
elements_to_f() click to toggle source
# File lib/matrix.rb, line 1435
def elements_to_f
  warn "Matrix#elements_to_f is deprecated, use map(&:to_f)", uplevel: 1
  map(&:to_f)
end
elements_to_i() click to toggle source
# File lib/matrix.rb, line 1440
def elements_to_i
  warn "Matrix#elements_to_i is deprecated, use map(&:to_i)", uplevel: 1
  map(&:to_i)
end
elements_to_r() click to toggle source
# File lib/matrix.rb, line 1445
def elements_to_r
  warn "Matrix#elements_to_r is deprecated, use map(&:to_r)", uplevel: 1
  map(&:to_r)
end
empty?() click to toggle source

Returns true if this is an empty matrix, i.e. if the number of rows or the number of columns is 0.

# File lib/matrix.rb, line 682
def empty?
  column_count == 0 || row_count == 0
end
entrywise_product(m)
Alias for: hadamard_product
eql?(other) click to toggle source
# File lib/matrix.rb, line 847
def eql?(other)
  return false unless Matrix === other &&
                      column_count == other.column_count # necessary for empty matrices
  rows.eql? other.rows
end
find_index(*args)
Alias for: index
first_minor(row, column) click to toggle source

Returns the submatrix obtained by deleting the specified row and column.

Matrix.diagonal(9, 5, -3, 4).first_minor(1, 2)
  => 9 0 0
     0 0 0
     0 0 4
# File lib/matrix.rb, line 585
def first_minor(row, column)
  raise RuntimeError, "first_minor of empty matrix is not defined" if empty?

  unless 0 <= row && row < row_count
    raise ArgumentError, "invalid row (#{row.inspect} for 0..#{row_count - 1})"
  end

  unless 0 <= column && column < column_count
    raise ArgumentError, "invalid column (#{column.inspect} for 0..#{column_count - 1})"
  end

  arrays = to_a
  arrays.delete_at(row)
  arrays.each do |array|
    array.delete_at(column)
  end

  new_matrix arrays, column_count - 1
end
hadamard_product(m) click to toggle source

Hadamard product

Matrix[[1,2], [3,4]].hadamard_product(Matrix[[1,2], [3,2]])
  => 1  4
     9  8
# File lib/matrix.rb, line 986
def hadamard_product(m)
  combine(m){|a, b| a * b}
end
Also aliased as: entrywise_product
hash() click to toggle source

Returns a hash-code for the matrix.

# File lib/matrix.rb, line 865
def hash
  @rows.hash
end
hermitian?() click to toggle source

Returns true if this is an hermitian matrix. Raises an error if matrix is not square.

# File lib/matrix.rb, line 690
def hermitian?
  Matrix.Raise ErrDimensionMismatch unless square?
  each_with_index(:upper).all? do |e, row, col|
    e == rows[col][row].conj
  end
end
hstack(*matrices) click to toggle source

Returns a new matrix resulting by stacking horizontally the receiver with the given matrices

x = Matrix[[1, 2], [3, 4]]
y = Matrix[[5, 6], [7, 8]]
x.hstack(y) # => Matrix[[1, 2, 5, 6], [3, 4, 7, 8]]
# File lib/matrix.rb, line 1198
def hstack(*matrices)
  self.class.hstack(self, *matrices)
end
imag()
Alias for: imaginary
imaginary() click to toggle source

Returns the imaginary part of the matrix.

Matrix[[Complex(1,2), Complex(0,1), 0], [1, 2, 3]]
  => 1+2i  i  0
        1  2  3
Matrix[[Complex(1,2), Complex(0,1), 0], [1, 2, 3]].imaginary
  =>   2i  i  0
        0  0  0
# File lib/matrix.rb, line 1354
def imaginary
  collect(&:imaginary)
end
Also aliased as: imag
index(value, selector = :all) → [row, column] click to toggle source
index(selector = :all){ block } → [row, column]
index(selector = :all) → an_enumerator

The index method is specialized to return the index as [row, column] It also accepts an optional selector argument, see each for details.

Matrix[ [1,2], [3,4] ].index(&:even?) # => [0, 1]
Matrix[ [1,1], [1,1] ].index(1, :strict_lower) # => [1, 0]
# File lib/matrix.rb, line 513
def index(*args)
  raise ArgumentError, "wrong number of arguments(#{args.size} for 0-2)" if args.size > 2
  which = (args.size == 2 || SELECTORS.include?(args.last)) ? args.pop : :all
  return to_enum :find_index, which, *args unless block_given? || args.size == 1
  if args.size == 1
    value = args.first
    each_with_index(which) do |e, row_index, col_index|
      return row_index, col_index if e == value
    end
  else
    each_with_index(which) do |e, row_index, col_index|
      return row_index, col_index if yield e
    end
  end
  nil
end
Also aliased as: find_index
inspect() click to toggle source

Overrides Object#inspect

# File lib/matrix.rb, line 1470
def inspect
  if empty?
    "#{self.class}.empty(#{row_count}, #{column_count})"
  else
    "#{self.class}#{@rows.inspect}"
  end
end
inv()
Alias for: inverse
inverse() click to toggle source

Returns the inverse of the matrix.

Matrix[[-1, -1], [0, -1]].inverse
  => -1  1
      0 -1
# File lib/matrix.rb, line 997
def inverse
  Matrix.Raise ErrDimensionMismatch unless square?
  self.class.I(row_count).send(:inverse_from, self)
end
Also aliased as: inv
laplace_expansion(row: nil, column: nil) click to toggle source

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]
# File lib/matrix.rb, line 644
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
Also aliased as: cofactor_expansion
lower_triangular?() click to toggle source

Returns true if this is a lower triangular matrix.

# File lib/matrix.rb, line 700
def lower_triangular?
  each(:strict_upper).all?(&:zero?)
end
lup() click to toggle source

Returns the LUP decomposition of the matrix; see LUPDecomposition.

a = Matrix[[1, 2], [3, 4]]
l, u, p = a.lup
l.lower_triangular? # => true
u.upper_triangular? # => true
p.permutation?      # => true
l * u == p * a      # => true
a.lup.solve([2, 5]) # => Vector[(1/1), (1/2)]
# File lib/matrix.rb, line 1322
def lup
  LUPDecomposition.new(self)
end
Also aliased as: lup_decomposition
lup_decomposition()
Alias for: lup
map()
Alias for: collect
minor(*param) click to toggle source

Returns a section of the matrix. The parameters are either:

  • start_row, nrows, start_col, ncols; OR

  • row_range, col_range

Matrix.diagonal(9, 5, -3).minor(0..1, 0..2)
  => 9 0 0
     0 5 0

Like Array#[], negative indices count backward from the end of the row or column (-1 is the last element). Returns nil if the starting row or column is greater than #row_count or #column_count respectively.

# File lib/matrix.rb, line 544
def minor(*param)
  case param.size
  when 2
    row_range, col_range = param
    from_row = row_range.first
    from_row += row_count if from_row < 0
    to_row = row_range.end
    to_row += row_count if to_row < 0
    to_row += 1 unless row_range.exclude_end?
    size_row = to_row - from_row

    from_col = col_range.first
    from_col += column_count if from_col < 0
    to_col = col_range.end
    to_col += column_count if to_col < 0
    to_col += 1 unless col_range.exclude_end?
    size_col = to_col - from_col
  when 4
    from_row, size_row, from_col, size_col = param
    return nil if size_row < 0 || size_col < 0
    from_row += row_count if from_row < 0
    from_col += column_count if from_col < 0
  else
    raise ArgumentError, param.inspect
  end

  return nil if from_row > row_count || from_col > column_count || from_row < 0 || from_col < 0
  rows = @rows[from_row, size_row].collect{|row|
    row[from_col, size_col]
  }
  new_matrix rows, [column_count - from_col, size_col].min
end
normal?() click to toggle source

Returns true if this is a normal matrix. Raises an error if matrix is not square.

# File lib/matrix.rb, line 708
def normal?
  Matrix.Raise ErrDimensionMismatch unless square?
  rows.each_with_index do |row_i, i|
    rows.each_with_index do |row_j, j|
      s = 0
      rows.each_with_index do |row_k, k|
        s += row_i[k] * row_j[k].conj - row_k[i].conj * row_k[j]
      end
      return false unless s == 0
    end
  end
  true
end
orthogonal?() click to toggle source

Returns true if this is an orthogonal matrix Raises an error if matrix is not square.

# File lib/matrix.rb, line 726
def orthogonal?
  Matrix.Raise ErrDimensionMismatch unless square?
  rows.each_with_index do |row, i|
    column_count.times do |j|
      s = 0
      row_count.times do |k|
        s += row[k] * rows[k][j]
      end
      return false unless s == (i == j ? 1 : 0)
    end
  end
  true
end
permutation?() click to toggle source

Returns true if this is a permutation matrix Raises an error if matrix is not square.

# File lib/matrix.rb, line 744
def permutation?
  Matrix.Raise ErrDimensionMismatch unless square?
  cols = Array.new(column_count)
  rows.each_with_index do |row, i|
    found = false
    row.each_with_index do |e, j|
      if e == 1
        return false if found || cols[j]
        found = cols[j] = true
      elsif e != 0
        return false
      end
    end
    return false unless found
  end
  true
end
rank() click to toggle source

Returns the rank of the matrix. Beware that using Float values can yield erroneous results because of their lack of precision. Consider using exact types like Rational or BigDecimal instead.

Matrix[[7,6], [3,9]].rank
  => 2
# File lib/matrix.rb, line 1211
def rank
  # We currently use Bareiss' multistep integer-preserving gaussian elimination
  # (see comments on determinant)
  a = to_a
  last_column = column_count - 1
  last_row = row_count - 1
  pivot_row = 0
  previous_pivot = 1
  0.upto(last_column) do |k|
    switch_row = (pivot_row .. last_row).find {|row|
      a[row][k] != 0
    }
    if switch_row
      a[switch_row], a[pivot_row] = a[pivot_row], a[switch_row] unless pivot_row == switch_row
      pivot = a[pivot_row][k]
      (pivot_row+1).upto(last_row) do |i|
         ai = a[i]
         (k+1).upto(last_column) do |j|
           ai[j] =  (pivot * ai[j] - ai[k] * a[pivot_row][j]) / previous_pivot
         end
       end
      pivot_row += 1
      previous_pivot = pivot
    end
  end
  pivot_row
end
rank_e() click to toggle source

deprecated; use #rank

# File lib/matrix.rb, line 1242
def rank_e
  warn "Matrix#rank_e is deprecated; use #rank", uplevel: 1
  rank
end
real() click to toggle source

Returns the real part of the matrix.

Matrix[[Complex(1,2), Complex(0,1), 0], [1, 2, 3]]
  => 1+2i  i  0
        1  2  3
Matrix[[Complex(1,2), Complex(0,1), 0], [1, 2, 3]].real
  =>    1  0  0
        1  2  3
# File lib/matrix.rb, line 1368
def real
  collect(&:real)
end
real?() click to toggle source

Returns true if all entries of the matrix are real.

# File lib/matrix.rb, line 765
def real?
  all?(&:real?)
end
rect() click to toggle source

Returns an array containing matrices corresponding to the real and imaginary parts of the matrix

m.rect == [m.real, m.imag] # ==> true for all matrices m

# File lib/matrix.rb, line 1378
def rect
  [real, imag]
end
Also aliased as: rectangular
rectangular()
Alias for: rect
regular?() click to toggle source

Returns true if this is a regular (i.e. non-singular) matrix.

# File lib/matrix.rb, line 772
def regular?
  not singular?
end
round(ndigits=0) click to toggle source

Returns a matrix with entries rounded to the given precision (see Float#round)

# File lib/matrix.rb, line 1250
def round(ndigits=0)
  map{|e| e.round(ndigits)}
end
row(i) { |e| ... } click to toggle source

Returns row vector number i of the matrix as a Vector (starting at 0 like an array). When a block is given, the elements of that vector are iterated.

# File lib/matrix.rb, line 329
def row(i, &block) # :yield: e
  if block_given?
    @rows.fetch(i){return self}.each(&block)
    self
  else
    Vector.elements(@rows.fetch(i){return nil})
  end
end
row_count() click to toggle source

Returns the number of rows.

# File lib/matrix.rb, line 314
def row_count
  @rows.size
end
Also aliased as: row_size
row_size()
Alias for: row_count
row_vectors() click to toggle source

Returns an array of the row vectors of the matrix. See Vector.

# File lib/matrix.rb, line 1406
def row_vectors
  Array.new(row_count) {|i|
    row(i)
  }
end
singular?() click to toggle source

Returns true if this is a singular matrix.

# File lib/matrix.rb, line 779
def singular?
  determinant == 0
end
square?() click to toggle source

Returns true if this is a square matrix.

# File lib/matrix.rb, line 786
def square?
  column_count == row_count
end
symmetric?() click to toggle source

Returns true if this is a symmetric matrix. Raises an error if matrix is not square.

# File lib/matrix.rb, line 794
def symmetric?
  Matrix.Raise ErrDimensionMismatch unless square?
  each_with_index(:strict_upper) do |e, row, col|
    return false if e != rows[col][row]
  end
  true
end
t()
Alias for: transpose
to_a() click to toggle source

Returns an array of arrays that describe the rows of the matrix.

# File lib/matrix.rb, line 1431
def to_a
  @rows.collect(&:dup)
end
to_matrix() click to toggle source

Explicit conversion to a Matrix. Returns self

# File lib/matrix.rb, line 1424
def to_matrix
  self
end
to_s() click to toggle source

Overrides Object#to_s

# File lib/matrix.rb, line 1457
def to_s
  if empty?
    "#{self.class}.empty(#{row_count}, #{column_count})"
  else
    "#{self.class}[" + @rows.collect{|row|
      "[" + row.collect{|e| e.to_s}.join(", ") + "]"
    }.join(", ")+"]"
  end
end
tr()
Alias for: trace
trace() click to toggle source

Returns the trace (sum of diagonal elements) of the matrix.

Matrix[[7,6], [3,9]].trace
  => 16
# File lib/matrix.rb, line 1259
def trace
  Matrix.Raise ErrDimensionMismatch unless square?
  (0...column_count).inject(0) do |tr, i|
    tr + @rows[i][i]
  end
end
Also aliased as: tr
transpose() click to toggle source

Returns the transpose of the matrix.

Matrix[[1,2], [3,4], [5,6]]
  => 1 2
     3 4
     5 6
Matrix[[1,2], [3,4], [5,6]].transpose
  => 1 3 5
     2 4 6
# File lib/matrix.rb, line 1277
def transpose
  return self.class.empty(column_count, 0) if row_count.zero?
  new_matrix @rows.transpose, row_count
end
Also aliased as: t
unitary?() click to toggle source

Returns true if this is a unitary matrix Raises an error if matrix is not square.

# File lib/matrix.rb, line 806
def unitary?
  Matrix.Raise ErrDimensionMismatch unless square?
  rows.each_with_index do |row, i|
    column_count.times do |j|
      s = 0
      row_count.times do |k|
        s += row[k].conj * rows[k][j]
      end
      return false unless s == (i == j ? 1 : 0)
    end
  end
  true
end
upper_triangular?() click to toggle source

Returns true if this is an upper triangular matrix.

# File lib/matrix.rb, line 823
def upper_triangular?
  each(:strict_lower).all?(&:zero?)
end
vstack(*matrices) click to toggle source

Returns a new matrix resulting by stacking vertically the receiver with the given matrices

x = Matrix[[1, 2], [3, 4]]
y = Matrix[[5, 6], [7, 8]]
x.vstack(y) # => Matrix[[1, 2], [3, 4], [5, 6], [7, 8]]
# File lib/matrix.rb, line 1291
def vstack(*matrices)
  self.class.vstack(self, *matrices)
end
zero?() click to toggle source

Returns true if this is a matrix with only zero elements

# File lib/matrix.rb, line 830
def zero?
  all?(&:zero?)
end

Private Instance Methods

[]=(i, j, v) click to toggle source
# File lib/matrix.rb, line 304
def []=(i, j, v)
  @rows[i][j] = v
end
Also aliased as: set_element, set_component
determinant_bareiss() click to toggle source

Private. Use #determinant

Returns the determinant of the matrix, using Bareiss' multistep integer-preserving gaussian elimination. It has the same computational cost order O(n^3) as standard Gaussian elimination. Intermediate results are fraction free and of lower complexity. A matrix of Integers will have thus intermediate results that are also Integers, with smaller bignums (if any), while a matrix of Float will usually have intermediate results with better precision.

# File lib/matrix.rb, line 1153
def determinant_bareiss
  size = row_count
  last = size - 1
  a = to_a
  no_pivot = Proc.new{ return 0 }
  sign = +1
  pivot = 1
  size.times do |k|
    previous_pivot = pivot
    if (pivot = a[k][k]) == 0
      switch = (k+1 ... size).find(no_pivot) {|row|
        a[row][k] != 0
      }
      a[switch], a[k] = a[k], a[switch]
      pivot = a[k][k]
      sign = -sign
    end
    (k+1).upto(last) do |i|
      ai = a[i]
      (k+1).upto(last) do |j|
        ai[j] =  (pivot * ai[j] - ai[k] * a[k][j]) / previous_pivot
      end
    end
  end
  sign * pivot
end
set_component(i, j, v)
Alias for: []=
set_element(i, j, v)
Alias for: []=