From: Jim Carter <jcarter@...>
Date: 2011-02-02T07:13:49+09:00
Subject: Re: Returning a column vector from a 2D array

Hope this isn't too fragmentary and of no use

Here is where I create class for generating 2D arrays

******
class Array2D

  require 'matrix'

  def initialize(row, column)   #this creates the 2D array structure
      @data = Array.new(row) { Array.new(column) {0}}   #initialize 
array with
                                                        #0's
  end

  def [](x, y)    #this allows one read access to cells within 2D array
      @data[x][y]
  end

  def []=(x, y, value)  #this allows one write access to cells within 2D 
array
     @data[x][y] = value
  end

end

******
In a separate class, ExteriorBallistics, in its method "calculate,"  I 
create a new array component

******
 nrows = ((los_rng - start_rng)/rng_incr).round

  # initialize arrays
    e = Array2D.new(nrows+1, 14)

******

Later I assign to the matrix e.  Putting puts in front of any of these 
assignments yields correct column values

******

 # Store Values at appropriate intervals (integral numbers of RangeInc)
        if ((range_ctr % rng_incr == 0)||(range_ctr == los_rng ))

          @index = (((rng_incr + range2 - start_rng)/rng_incr) - 1).ceil

          e[@index,RANGE] = range2
          e[@index,VELOCITY] = vel
          e[@index,TIME] = time1
          e[@index,PATH] = height1 * 12      # %path, converted to 
inches
          e[@index,DEFLECTION] = deflection1 * 12  # %convert to inches
          e[@index,ENERGY] = energy
          e[@index,DROP] = drop
          e[@index,MOA] = moa
          e[@index,ADJ_PATH] = adj_path
          e[@index,EQV_DROP] = eqv_drop
          e[@index,MOMENTUM] = momentum
          e[@index,TAYLOR_KO] = taylor_ko
          e[@index,OGW] = optimal_game_weight


        end  #  if (range_ctr % rng_incr == 0)

*******

@index gives me the column length once the entire routine is complete.
Towards the end of the "calculate" method, once all elements have been 
assigned to the matrix, I make the following association

*******

@data_array = e

*******

Furthermore, under the same class ExteriorBallistics, I declare an 
attr_accessor :data_array

Then I want to run calculate via

ExteriorBallistics.new do

  {a bunch of assignments here}

  calculate

  ary_length = @index  #returns the correct column length
  puts @data_array

This returns the Array ID.

I can do a .inspect to have the entire matrix printed out in string 
format, but I really want column numeric values.

Strangely, if I do either this @data_array[0..ary_length,0] or this 
@data_array[0,0..ary_length], I get the exact same result, which is the 
first ROW spanning all columns that I created.

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