Working with matrices and vectors in Ruby before has been annoying because methods I expected to find were not there, and there wasn’t much documentation. Here, I present some simple additions to the `Matrix` and `Vector` classes that I found helpful.

 ```1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 ``` ```require 'matrix' class Matrix # Assign the given value to the slot at the specified row and column def []=(row, column, value) @rows[row][column] = value end # Create an n by n matrix where each slot is initialized to the given value def Matrix.square(n, value) matrix = Matrix.zero(n) (0...n).each do |row| (0...n).each do |col| matrix[row, col] = value end end matrix end # Create an m by n matrix where each slot is initialized to the given value def Matrix.fill(m, n, value) rows = [] m.times do row = [] n.times { row << value } rows << row end Matrix.rows(rows) end # Returns a pretty string representation of the matrix def to_s [sprintf("%d x %d Matrix", @rows.length, column_size), @rows.map { |row| row.inspect }].flatten.join("\n") end end class Vector # Iterate over all elements in the vector def each raise ArgumentError unless block_given? @elements.each { |element| yield element } end # Returns true if the vector includes the given item def include?(other) to_a.include? other end end ```

Here are some examples of how to use the new methods:

 ```1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 ``` ```irb(main):039:0> matrix = Matrix.square(3, 'a') => Matrix[["a", "a", "a"], ["a", "a", "a"], ["a", "a", "a"]] irb(main):040:0> puts matrix 3 x 3 Matrix ["a", "a", "a"] ["a", "a", "a"] ["a", "a", "a"] => nil irb(main):041:0> other_matrix = Matrix.fill(2, 3, 'b') => Matrix[["b", "b", "b"], ["b", "b", "b"]] irb(main):042:0> other_matrix[1, 2] = 'new value' => "new value" irb(main):043:0> puts other_matrix 2 x 3 Matrix ["b", "b", "b"] ["b", "b", "new value"] => nil irb(main):055:0> other_matrix.row_vectors.each { |row| row.each { |el| puts el } } b b b b b new value => [Vector["b", "b", "b"], Vector["b", "b", "new value"]] irb(main):056:0> num_matrix = Matrix.square(3, 0) => Matrix[[0, 0, 0], [0, 0, 0], [0, 0, 0]] irb(main):057:0> num_matrix[0, 1] = 1 => 1 irb(main):058:0> num_matrix[0, 2] = 2 => 2 irb(main):059:0> num_matrix[1, 0] = 3 => 3 irb(main):060:0> num_matrix[1, 1] = 4 => 4 irb(main):061:0> puts num_matrix 3 x 3 Matrix [0, 1, 2] [3, 4, 0] [0, 0, 0] => nil irb(main):062:0> num_matrix.row_vectors.select { |row| row.include? 4 } => [Vector[3, 4, 0]] ```