# ExMatrix
  
ExMatrix is an Elixir library implementing a parallel matrix multiplication algorithm with other utilities for working with matrices.
### Installation
The latest version is `0.0.1` and requires Elixir `~> 1.0`.
Releases are published through [hex.pm](https://hex.pm/packages/exmatrix). Add as a dependency in your `mix.exs` file:
```elixir
defp deps do
[ { :exmatrix, "~> 0.0.1" } ]
end
```
### Matrices
Matrices are expected to be lists of lists of numbers, so for example, a simple 2x2 matrix might look like
```elixir
iex> matrix = [[0, 0], [1,1]]
[[0, 0], [1,1]]
```
To get an empty matrix you can use ```new_matrix``` to generate a zero-filled matrix
```elixir
iex> ExMatrix.new_matrix(2,2)
[[0, 0], [0,0]]
```
To test out the library, you can generate a random matrix using ```random_cells``` by passing the number of rows, columns and a maximum value to be contained in each cell.
```elixir
iex> random_cells(2, 2, 10)
[[3, 4], [9, 0]]
```
### Multiplication
To multiply two matrices together you can call either ```multiply``` or ```pmultiply``` if you wish to do the multiplication in parallel.
```elixir
iex> matrix_a = [[2,3], [3,5]]
[[2,3], [3,5]]
iex> matrix_b = [[1,2], [5,-1]]
[[1,2], [5,-1]]
iex> ExMatrix.muliply(matrix_a, matrix_b)
[[17, 1], [28, 1]]
```
### Addition
Addition of matrices happens as you might expect, with the ```add``` function
```elixir
iex> matrix_a = [[0, 1, 2], [9, 8, 7]]
[[0, 1, 2], [9, 8, 7]]
iex> matrix_b = [[6, 5, 4], [3, 4, 5]]
[[6, 5, 4], [3, 4, 5]]
iex> ExMatrix.add(matrix_a, matrix_b)
[[6, 6, 6], [12, 12, 12]]
```
If you provide two matrices where the number of rows or columns differs, then an ```ArgumentError``` is raised.
### Subtraction
Subtraction is performed on two matrices (which must have the same dimentions) by using the ```subtract``` function
```elixir
iex> matrix_a = [[0, 1, 2], [9, 8, 7]]
[[0, 1, 2], [9, 8, 7]]
iex> from_matrix = [[6, 5, 4], [3, 4, 5]]
[[6, 5, 4], [3, 4, 5]]
iex> ExMatrix.subtract(matrix_a, from_matrix)
[[-6, -4, -2], [6, 4, 2]]
```
If you provide two matrices where the number of rows or columns differs, then an ```ArgumentError``` is raised.
### Utility functions
#### Size
The ```size``` function will return the number of rows and columns in your matrix.
```elixir
iex> {rows, cols} = ExMatrix.size([[1,2,3], [4, 5, 6], [7, 8, 9]])
{3, 3}
iex> rows
3
```
#### Transpose
You can transpose a matrix so that the columns become rows (rotating the matrix by 90 degrees).
```elixir
iex> ExMatrix.transpose([[1,2,3], [4, 5, 6], [7, 8, 9]])
[[1, 4, 7], [2, 5, 8], [3, 6, 9]]
```
### License
```
Copyright 2015 A115 Ltd
Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at
http://www.apache.org/licenses/LICENSE-2.0
Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
```
