From: Masahiro TANAKA <masa16.tanaka@...>
Date: 2010-04-27T22:52:19+09:00
Subject: Re: Populate (an array or a matrix) from a vector

Hi,

Paul A.  wrote:
> And now, if the seeder vector is: [1, 0], the result should be:
>
> => [
> =>   [4, 3, 2, 1, 0],
> =>   [4, 3, 2, 1, 0],
> =>   [4, 3, 2, 1, 0]
> => ]

I guessed your intention and wrote it using NArray:

require 'narray'

def populate( shape, v )
  ndim = shape.size
  max = shape.max
  a = NArray.int(ndim,*shape)
  shape.each_with_index do |sz,i|
    if v[i] == 0
      a[i,false] = max
    else
      r = [1]*ndim
      r[i] = sz
      x = NArray.int(sz).indgen!
      x = sz-1-x if v[i] > 0
      x /= v[i].abs
      a[i,false] = x.reshape!(*r)
    end
  end
  a.min(0)
end

populate( [5,3], [1,0] )
=> NArray.int(5,3):
[ [ 4, 3, 2, 1, 0 ],
  [ 4, 3, 2, 1, 0 ],
  [ 4, 3, 2, 1, 0 ] ]

populate( [5,3], [-1,0] )
=> NArray.int(5,3):
[ [ 0, 1, 2, 3, 4 ],
  [ 0, 1, 2, 3, 4 ],
  [ 0, 1, 2, 3, 4 ] ]

populate( [5,3], [-2,0] )
=> NArray.int(5,3):
[ [ 0, 0, 1, 1, 2 ],
  [ 0, 0, 1, 1, 2 ],
  [ 0, 0, 1, 1, 2 ] ]

populate( [5,3], [1,1] )
=> NArray.int(5,3):
[ [ 2, 2, 2, 1, 0 ],
  [ 1, 1, 1, 1, 0 ],
  [ 0, 0, 0, 0, 0 ] ]

populate( [5,3], [0,1] )
=> NArray.int(5,3):
[ [ 2, 2, 2, 2, 2 ],
  [ 1, 1, 1, 1, 1 ],
  [ 0, 0, 0, 0, 0 ] ]

populate( [5,3,3], [2,1,1] )
=> NArray.int(5,3,3):
[ [ [ 2, 1, 1, 0, 0 ],
    [ 1, 1, 1, 0, 0 ],
    [ 0, 0, 0, 0, 0 ] ],
  [ [ 1, 1, 1, 0, 0 ],
    [ 1, 1, 1, 0, 0 ],
    [ 0, 0, 0, 0, 0 ] ],
  [ [ 0, 0, 0, 0, 0 ],
    [ 0, 0, 0, 0, 0 ],
    [ 0, 0, 0, 0, 0 ] ] ]

Masahiro Tanaka