add a row to matrix - http://stackoverflow.com/questions/16011252/add-a-row-array-to-an-empty-matrix

ruby_add_row_matrix.rb

2.0.0p0 :001 > require 'matrix'
 => true 
2.0.0p0 :002 > m = Matrix[]
 => Matrix.empty(0, 0) 
2.0.0p0 :003 > m = Matrix.rows(m.to_a << [1,2,3])
 => Matrix[[1, 2, 3]] 
2.0.0p0 :004 > m = Matrix.rows(m.to_a << [2,3,4])
 => Matrix[[1, 2, 3], [2, 3, 4]]