From: Ryan Davis <ryand-ruby@...>
Date: 2012-10-03T05:14:22+09:00
Subject: Re: 2D array strategies


On Oct 2, 2012, at 11:49 , Thomas Luedeke <lists@ruby-forum.com> wrote:

> Since Ruby only does 1D arrays, is there a trick for an array of arrays?
> Or is this hash territory?  How do I do the 2D equivalent of using the
> .push array command to add on more data to the original array?  Are
> there are any particular Ruby resources that I need to go read up on and
> go practice in IRB?

Unless your dimensions are quite huge, you might want to try out Matrix:

% ri Matrix
= MMaattrriixx  <<  OObbjjeecctt

(from ruby core)
------------------------------------------------------------------------------
The Matrix class represents a mathematical matrix, and provides methods for
creating special-case matrices (zero, identity, diagonal, singular, vector),
operating on them arithmetically and algebraically, and determining their
mathematical properties (trace, rank, inverse, determinant).

Note that although matrices should theoretically be rectangular, this is not
enforced by the class.

Also note that the determinant of integer matrices may be incorrectly
calculated unless you also require 'mathn'.  This may be fixed in the future.

== MMeetthhoodd  CCaattaalloogguuee

To create a matrix:
*  Matrix[*rows]                  
*  Matrix.[](*rows)               
*  Matrix.rows(rows, copy = true) 
*  Matrix.columns(columns)        
*  Matrix.diagonal(*values)       
*  Matrix.scalar(n, value)        
*  Matrix.scalar(n, value)        
*  Matrix.identity(n)             
*  Matrix.unit(n)                 
*  Matrix.I(n)                    
*  Matrix.zero(n)                 
*  Matrix.row_vector(row)         
*  Matrix.column_vector(column)   

To access Matrix elements/columns/rows/submatrices/properties: 
*   [](i, j)                      
*  #row_size                      
*  #column_size                   
*  #row(i)                        
*  #column(j)                     
*  #collect                       
*  #map                           
*  #minor(*param)                 

Properties of a matrix:
*  #regular?                      
*  #singular?                     
*  #square?                       

Matrix arithmetic:
*   *(m)                          
*   +(m)                          
*   -(m)                          
*  #/(m)                          
*  #inverse                       
*  #inv                           
*   **                            

Matrix functions:
*  #determinant                   
*  #det                           
*  #rank                          
*  #trace                         
*  #tr                            
*  #transpose                     
*  #t                             

Conversion to other data types:
*  #coerce(other)                 
*  #row_vectors                   
*  #column_vectors                
*  #to_a                          

String representations:
*  #to_s                          
*  #inspect                       
------------------------------------------------------------------------------
= CCllaassss  mmeetthhooddss::

  I
  []
  column_vector
  columns
  diagonal
  identity
  new
  row_vector
  rows
  scalar
  unit
  zero

= IInnssttaannccee  mmeetthhooddss::

  *
  **
  +
  -
  /
  ==
  []
  clone
  coerce
  collect
  column
  column_size
  column_vectors
  compare_by_row_vectors
  det
  determinant
  eql?
  hash
  init_rows
  inspect
  inv
  inverse
  inverse_from
  map
  minor
  rank
  regular?
  row
  row_size
  row_vectors
  singular?
  square?
  t
  to_a
  to_s
  tr
  trace
  transpose