linalg

Library that makes it easy to do linear algebra in Crystal.

For now Linalg only supports Number::Primitive types.

Installation

1. Add the dependency to your shard.yml:

   dependencies:
     linalg:
       github: henrikac/linalg
   

2. Run shards install

Usage

Vector

Basic vector usage

require "linalg"

vec1 = Linalg::Vector.new([5, 10, 15])
vec2 = Linalg::Vector.new([10, 10, 10])

vec_add = vec1 + vec2
vec_add # => [15, 20, 25]

vec_sub = vec1 - vec2
vec_sub # => [-5, 0, 5]

scaled_vec = vec1 * 3

scaled_vec.each do |elem|
  puts elem
end

# will output
# 15
# 30
# 45

Zero vector

require "linalg"

empty_vec = Linalg::Vector(Int32).new
zero_vec = Linalg::Vector(Int32).new(5)
zero_vec # => [0, 0, 0, 0, 0]

zero_vec.zero? # => true
empty_vec.zero? # => false

Matrix

Basic matrix usage

require "linalg"

mat1 = Linalg::Matrix.new([[1, 2, 3], [4, 5, 6]])
mat2 = Linalg::Matrix.new([[1.0, 2.0], [3.0, 4.0]])

mat1 << Linalg::Vector.new([7, 8, 9])
mat2 << [5.0, 6.0]

mat1 # => [[1, 2, 3], [4, 5, 6], [7, 8, 9]]
mat2 # => [[1.0, 2.0], [3.0, 4.0], [5.0, 6.0]]

mat2.rows # => 3
mat2.columns # => 2

mat1[1] # => [4, 5, 6]
mat1[2, 0] # => 7

mat1 * 2 # => [[2, 4, 6], [8, 10, 12], [14, 16, 18]]

Matrix columns

require "linalg"

mat = Linalg::Matrix.new([[1, 2, 3], [4, 5, 6], [7, 8, 9]])

mat.get_column(0) # => [1, 4, 7]
mat.get_column(1) # => [2, 5, 8]
mat.get_column(2) # => [3, 6, 9]

mat.append_column([4, 7, 10])
mat # => [[1, 2, 3, 4], [4, 5, 6, 7], [7, 8, 9, 10]]

vec = Linalg::Vector.new([5, 8, 11])

mat.append_column(vec)
mat # => [[1, 2, 3, 4, 5], [4, 5, 6, 7, 8], [7, 8, 9, 10, 11]]

Identity and zero matrix

require "linalg"

zero_mat = Linalg::Matrix(Int32).new(3, 4)
identity_mat = Linalg::Matrix(Int32).new(3)

zero_mat # => [[0, 0, 0, 0], [0, 0, 0, 0], [0, 0, 0, 0]]
identity_mat # => [[1, 0, 0], [0, 1, 0], [0, 0, 1]]

zero_mat.zero? # => true
identity_mat.zero? # => false

zero_mat.identity? # => false
identity_mat.identity? # => true

Matrix addition and subtraction

Matrix addition and subtraction requires that both matrices and the dimensions, e.g. if matrix A is a m x n matrix then matrix B must also be m x n matrix.

require "linalg"

mat1 = Linalg::Matrix.new([[1, 2, 3], [4, 5, 6], [7, 8, 9]])
mat2 = Linalg::Matrix.new([[4, -1, 6], [2, 9, -3], [-4, 5, 1]])

mat3 = mat1 + mat2
mat3 # => [[5, 1, 9], [6, 14, 3], [3, 13, 10]]

mat4 = mat1 - mat2
mat4 # => [[-3, 3, -3], [2, -4, 9], [11, 3, 8]]

Matrix-vector and vector-matrix multiplication

For matrix-vector multiplication the vector must have the same size as the number of columns in the matrix.

require "linalg"

vec = Linalg::Vector.new([2, 3, 4])
mat = Linalg::Matrix.new([[5, 2, 6], [7, 2, 5], [1, 4, 2]])
mat * vec # => [40, 40, 22]

Vector-matrix multiplication requires the vector to have the same size as the number of rows in the matrix.

require "linalg"

vec = Linalg::Vector.new([2, 3, 4])
mat = Linalg::Matrix.new([[5, 2, 6], [7, 2, 5], [1, 4, 2]])
vec * mat # => [35, 26, 35]

Contributing

1. Fork it (https://github.com/henrikac/linalg/fork)
2. Create your feature branch (git checkout -b my-new-feature)
3. Commit your changes (git commit -am 'Add some feature')
4. Push to the branch (git push origin my-new-feature)
5. Create a new Pull Request

Contributors

• Henrik Christensen - creator and maintainer