SparseMatrix 
Build a sparce matrix from dense matrix
RubyGems
https://rubygems.org/gems/sparse_matrix
Tree
.
Installation
Add this line to your application's Gemfile:
gem 'sparse_matrix'
And then execute:
$ bundle
Or install it yourself as:
$ gem install sparse_matrix
Usage
as soon as
Authors
Kevin Robayna
Jose Antonio Rodriguez Leandro